我就不给你用机器翻译了，没意思，给你再外国网站找了个剧情介绍。
Once upon a time, a narrator informs the audience, there was a beautiful princess who had fallen under a curse that transformed her into an ogre every night at sundown. Her fairy godmother told her parents to lock her in a tower guarded by a terrible, fire-breathing dragon until her true love could rescue her and break her from the spell with his kiss. A man in armor, Prince Charming (also the narrator in the first scenes), is shown racing to the castle through adverse conditions, climbing to the Princess’ room—only to find the Big Bad Wolf lounging in the bed and reading a magazine. Princess Fiona is already rescued, married, and on her honeymoon.
Soon after the events of the first movie, the ogre Shrek and his wife Fiona return from their honeymoon to find Shrek's best friend Donkey in Shrek’s home, where they learn that he and Fiona's dragon guardian are having relationship problems and Dragon has become moody, so Donkey has moved out for the time being. Shrek doesn't want Donkey to live with him now that he's married[clarify]. As Shrek throws Donkey out, heralds from the kingdom of Far Far Away arrive to invite the Princess Fiona and Shrek to receive the blessing of her royal parents. Shrek balks and claims that her parents aren’t likely to accept him, but after a brief but heated argument, the couple and Donkey depart for Far Far Away. For days, the trip bores Donkey and he constantly asks "Are we there yet?" The travellers eventually arrive in the kingdom and meet with Fiona's parents, King Harold and Queen Lilian.
King Harold, Fiona’s father, confirms Shrek’s fears and becomes extremely angry when he discovers the truth about his daughter’s new husband, even though Queen Lilian is okay with it. As Harold and Lillian settle down to go to sleep after a dinner argument, Fiona returns, crying, to her room. There, her Fairy Godmother appears, and after being somewhat surprised by Fiona’s ogre-like appearance, promises to make everything better. Shrek then appears and Godmother realizes what has happened, causing her to leave in something of a hurry.
Shortly thereafter, Harold is visited by the Fairy Godmother. She is angry with Harold for "allowing" the marriage to take place (despite his having had no control over it), and it is revealed that her son, Prince Charming, was supposed to marry Fiona as part of a deal between the Fairy Godmother and King Harold. As they stop at a fast food restaurant, the Fairy Godmother subtly suggests that Harold have Shrek killed, and Harold heads to an unsavory pub called the Poison Apple Bar to hire the "ogre killer" he was looking for.
Back at the castle, and after Shrek looks at Fiona's childhood diary and learns that she will live happily ever after with Prince Charming, Harold says that he wishes to get a better start on his relationship with Shrek and tells him to meet him in the woods the next day "to go hunting." There, Shrek and Donkey are jumped by the King’s ogre-assassin, Puss in Boots. After Shrek foils Puss’ attack, Puss swears his life to Shrek, in thanks for Shrek sparing him. Taking an idea from Fairy Godmother’s business card (which was left with Fiona), the three decide to head to the Fairy Godmother’s office, which turns out to be a huge factory. They walk in on the Fairy Godmother preparing a potion, and are promptly dismissed after Fairy Godmother tells Shrek that there are no happy endings for ogres. Shrek and his friends disguise themselves as employees and break into the potion room. They set off an alarm and barely escape Fairy Godmother’s guards, but not before making off with a "Happily Ever After" potion.
Shrek, Donkey, and Puss begin walking back to Far Far Away. After some discussion, Shrek decides to drink the potion, but Donkey drinks it first to make sure it’s safe. After nothing immediately happens to him, Shrek finishes off the bottle but nothing happens, at least at first. It begins to rain and the three take shelter in a nearby barn. Donkey tries to cheer his best friend up by singing a song but he suddenly collapses followed shortly by Shrek. Back at the castle, Fiona is worried about Shrek, who had left very early in the morning to meet Harold in the woods, and informs her parents she will find Shrek and they will go back to the swamp where they belong. However, at the door to the castle, she also collapses and is taken to her room by her parents.
During the rainy night, Shrek, Donkey, and Fiona undergo a massive transformation that is not revealed until the next morning: Shrek becomes a handsome prince, Donkey is turned into a stunning white stallion, and Fiona is turned back into her original human appearance from the first movie. Shrek rides off to Fiona’s parents' castle to greet her. However, at the castle, Shrek makes his way to Fiona's room and she makes her way to the castle entrance, but they have taken different routes and pass by each other. Inside Fiona’s room, the Fairy Godmother traps Shrek, while Prince Charming introduces himself to Fiona as the new, transformed Shrek. Fiona is initially confused, but uneasily accepts this as the truth. Shrek, watching from the window as Fiona and Charming hug and then go back inside the castle with Fiona's parents, becomes dejected. He then takes the Fairy Godmother’s advice to let Fiona go and leaves.
Donkey, Shrek, and Puss are all sitting dejected at the Poison Apple (the pub where Harold hired Puss) when Shrek spots a cloaked Harold sneaking into a private meeting room. He, Donkey and Puss go outside to spy through the window. They find out that Harold is meeting with Charming and the Fairy Godmother, who explain that Harold must slip Fiona a love potion so that when she kisses Charming, she will fall in love with him. Harold refuses until the Fairy Godmother threatens to take away his own "happily ever after." Shrek, Donkey, and Puss watch quietly from outside the window, but when Charming addresses Fairy Godmother as “mother,” Donkey blows their cover. Shrek and his friends flee while the Fairy Godmother sends her men-at-arms after them.
Back at Shrek’s swamp, several of Shrek's friends from the first movie, the Three Blind Mice, the Three Little Pigs, the Big Bad Wolf, the Gingerbread Man, and Pinocchio, are watching a broadcast of the red carpet at the royal wedding ball, using the Magic Mirror as a television. They catch a promo for an upcoming episode of KNIGHTS (a parody of COPS) which shows a white stallion, an orange cat, and a handsome man being chased and finally arrested. Shrek’s friends notice that these perpetrators are Shrek, Donkey, and Puss. The three are thrown into the prison wagon as Shrek identifies himself madly and asks for Fiona. Shrek's friends in the swamp set out for Far Far Away to rescue him.
Meanwhile, Fiona is nervous about the upcoming wedding ball, citing displeasure with the "changes" in Charming as Shrek. Harold brings two cups of tea to her room (one of which is laced with love potion) and has a heart-to-heart with her in which she explains that she loved the old, "ugly," uncouth Shrek for who he was. As she reaches for a cup of tea, Harold stops her and takes the cup she was going to drink from, explaining that he drinks decaffeinated or it will keep him up at night.
Shrek, Donkey, and Puss have been sprung by Shrek's friends from the deepest, darkest dungeon, and they devise a plan to storm the castle and stop the royal ball. They head to Drury Lane where they have the Muffin Man, the Gingerbread Man's creator, make them a giant (though mentally simple) gingerbread man named Mongo. As Shrek rides Mongo to the castle to break in, Prince Charming begins dancing with Fiona and forcibly trying to kiss her (to activate the love potion), but she keeps rebuffing him. Shrek makes it into the castle (though Mongo is doused with boiling milk and falls into the moat, where Gingerbread Man is left to mourn) and lets the others in. Then, along with Puss and Donkey, Shrek races his way to the courtyard where the ball was taking place. The castle knights give chase, and Puss falls back to repay his debt to Shrek by holding them off so that Shrek may continue.
Just as Charming is about to kiss Fiona, Shrek arrives and stops them, enraging the Fairy Godmother. A struggle ensues in which many parties fumble to get Fairy Godmother’s wand away from her, but Donkey and Puss eventually get ahold of it. She uses a last ditch maneuver and tells Charming to kiss Fiona. It appears as though the love potion took effect, but when Fiona headbutts Charming, Harold reveals that he never gave her the potion. While Shrek and Fiona are reunited, Prince Charming gets ahold of the wand and tosses it to the Fairy Godmother. She proceeds to turn on Shrek, claiming once again that there are no happy endings for ogres. She sends a lethal bolt of magical energy at him, but King Harold dives in front to save Shrek and is hit instead, sacrificing himself. The bolt also reflects off of his reflective metal breastplate and strikes the Fairy Godmother, causing her to turn into dozens of bubbles that pop and rain on the ground. King Harold is thought to be killed by the bolt of energy but since the bolt was only magic[clarify], he was transformed into a bullfrog. Harold reveals that he is the Frog Prince, whom the Fairy Godmother transformed into a human years ago so that he could win the love of Queen Lillian. Shrek and Fiona accept his "old frog's apologies" for his behavior and he gives his royal blessing. Lillian forgives Harold and still accepts him as her husband.
As the clock strikes midnight, Shrek tells Fiona that if they kiss, they will remain as they are. Fiona tells Shrek that she loved him for who he was and that he didn't need to change for her. Within a matter of seconds, the potion wears off and Shrek and Fiona begin to transform back into their ogre forms. The potion also makes Donkey, to his dismay, turn back to his original appearance, but Shrek cheers him up by saying that Donkey looks like a real noble steed to his best friend. The movie, like its predecessor, ends with a musical montage, with cast members (led by Puss and Donkey) singing and dancing to Ricky Martin’s "Livin' La Vida Loca."
Before part of the credits roll, a lonely-feeling Donkey is shown alone crying and singing "All By Myself." Puss tries to cheer him up but he is just not in the mood to hang out with him. Dragon arrives at the area and is reconciled with Donkey. Then, Dragon shows her husband a group of six dragon-like donkey hybrid babies called dronkeys, implying that her previous moodiness were actually signs of pregnancy. After the screen turns black, Donkey comically says, "I gotta get a job."
参考资料：http://en.wikipedia.org/wiki/Shrek2#Plot