基本用法
中间只能用形容词或副词的原级，不能用比较级或最高级。如果在第二个as之后使用独立的人称代词，一般说来用主格(较正式)或宾格(非正式)均可。如：
He’s as old as she [her]. 他年纪跟她一样大。
但是，若第二个as之后的人称代词跟有谓语动词，则该人称代词只能用主格。如：
He is as old as she is.
但是有时用主格或宾格含义差别很大：
You love him as much as I (=as I love him). 你爱他像我爱他一样。
You love him as much as me (=as you love me). 你爱他像爱我一样。
用于否定句
在肯定句中用as…as, 在否定句中用not as…as或not so…as 均可。如：
He doesn’t study as [so] hard as his brother. 他学习不如他弟弟努力。
关于比较对象
使用该结构要注意比较对象的一致性，即比较的双方必须是可以比较的同类人或物，否则会出错。如：
你的房间与我的一样大。
正：Your room is as large as mine
误：Your room is as large as me.
涉及数量或程度
如果涉及数量或程度可用：as much+ (不可数名词+) as / as many+ (可数名词复数+) as。如：
You must speak English as much as possible. 你必须尽可能地多说英语。
You’ve made as many mistakes as I have. 你犯的错误和我犯的一样多。
注意下列结构的词序
她和她妈妈一样是位好厨师。
正：She is a cook as good as her mother.
正：She is as good a cook as her mother.
误：She is as a good cook as her mother.
关于修饰语
修饰as…as结构的常见词语有nearly, almost, just, exactly, half, quite, twice, three times等，请注意这些修饰语都只能放在as…as 结构之前 (而不能置于其中或其后。如：
I earn half as much as you do. 我只赚你的一半钱。
This rope is twice as long as that one. 这根绳子比那根长一倍。
省略用法
as…as结构在一定的上下文中可以用其省略结构(即省去其中的一个 as)。如：
She’s clever, but her brother is just as clever. 她很聪明，但她兄弟也一样聪明。
The woman married a man poor as herself. 这个女人嫁给了一个与她一样穷的男人。
当语境背景谈的是两个不同的人或事物在某一个方面进行物比较时，as…as…结构可译为“像……一样”。如：
You can get there just as cheaply by air as by train. 你坐飞机到那里同坐火车一样便宜。
In many sports physical fitness is not as important as technique. 在许多体育运动中，体能没有技巧重要。
Some of the doctors are paid almost twice as much as the nurses. 有些医生所获得的报酬差不多是护士的两倍。
当语境背景谈的是同一个人或事物在某两个不同的方面进行物比较时，as…as…结构的用法与both…and…相似，通常可译为“既……又……”。如：
He was as sensitive as he was obstinate. 他既敏感又固执。
Martin was as impatient as he was stubborn. 马丁既缺乏耐心又很顽固。
The confession was proved to be as absurd as it was false. 这份供词被证明是既虚假，又荒谬。
当语境背景谈的是两个不同的人或事物在某两个不同的方面进行物比较时，as…as…结构的用法与whereas相似，通常可译为“而”。如：
He is as kind as his sister is honest. 他的妹妹很诚实，而他则很和蔼可亲。
The prisons are as over-crowded as the farmlands are empty. 监狱里人满为患，而田地却无人耕种。
用于as…as possible 与 as…as one can结构时，通常可译为“尽量”“尽可能”“拼命地”。如：
I want it (to be) done as quickly as possible. 我希望这件事尽快做好。
Dictionaries should be as user-friendly as possible. 词典应尽可能便于使用。
Perishables need to be consumed as quickly as possible. 易腐烂的食物要尽快吃掉。
用于as…as can [could] be结构时，通常可译为“极其”“非常”“要多……就多……”。如：
Both houses were as clean as could be. 两座房子都极其干净。
A：What was the weather like on your holiday? 你度假时天气怎么样?
B：It was as good as could be expected. 好得很。
表示：和... 一样
如：Mary is as clever as her sister.
Mary writes as carefully as her sister.