1．原级用法
① 表示被比较双方在某一方面相等或相同时, 用as + adj / adv + as结构, 表示“…和…一样” 。如：
a. Xiao Li is as tall as his sister.
b. It is as cold today as it was yesterday.
c. There are as many seats in this hall as in that hall.
② 表示被比较双方在某一方面不相等或不同时, 用not as / so + adj / adv + as, 表示“…和…不一样”
a. Xiao Li is not as / so tall as his brother.
b. It is not so / as cold today as yesterday.
c. There are not so / as many seats in this hall as in that hall.

　　2．比较级的用法
① 对方比较，表示一方超过另一方时，用“比较级 + than”的结构表示。如：
This picture is more beautiful than that one.
② 表示一方不及另一方时，用“less + 原级 + than”的结构表示。如：
This room is less beautiful than that one.
③ 表示一方超过另一方的程度或数量时，可在比较级前加表示程度的状语，如even、a lot、a bit、a little、still、much、far、yet、by fay等修饰。如：
He works even harder than before.
注意：英语的比较级前如无even、still或yet等时，译成汉语时可用“较”或“…一些”或不译出，一般不可有“更”。如：
She is better than she was yesterday.
Please come earlier tomorrow.
另注意：by far通常用于强调最高级。用于比较级时，一般放在比较级的后面，如在前面，应在二者中间加“the”。如：
He is taller by far than his brother.
He is by far the taller of the two brothers.
④ 表示一方随另一方的程度而变化时，用“the + 比较级（主语 + 谓语），the + 比较级（主语 + 谓语）”的结构（意为“越……越……”）。如：
The harder he works, the happier he feels.
⑤ 不与其他事物相比，表示本身程度的改变时，用“比较级 + and + 比较级”的结构。如：
The weather is getting colder and colder.
The girl becomes more and more beautiful.
⑥ 某些以-ior结尾的形容词进行比较时，用to代替than。这些词有inferior（劣等的，次的）、superior（较好的，优于……）、junior（资历较浅的）、senior（资格较老的）、prior（在……之前）等。
He is superior to Mr. Zhang in chemistry.
⑦ 在比较从句中为了避免重复，我们通常用that(those)、one(ones)代替前面出现的名词。that指物,one既可指人又可指物。that可代替可数名词单数和不可数名词，而one只能代替可数名词。
The book on the table is more interesting than that(或the one)on the desk.
A box made of steel is stronger than one made of wood.
⑧ 倍数表达法。
（A）A is three(four, etc.)times the size(height, length etc.)of B.
如：The new building is four times the size(the height)of the old one. 
（B）A is three(four, etc.)times as big(high, long, etc.)as B.
如：Asia is four times as large as Europe. 
（C）A is three (four, etc.)times bigger(higher, longer, etc.)than B.
如：Your school is three times bigger than ours. 
用times 表倍数通常用于三倍以上，两倍可以用twice或double.

3．最高级的用法
①三者或三者以上相比，表示最高程度时，用“the + 最高级”的结构表示。这种句式一般常有表示比较范围的介词短语。如：
Zhang Hua is the tallest of the three.
He works(the)hardest in his class.
②最高级可被序数词以及much、by far、nearly、almost 、by no means、not quite、not really、nothing like等词语所修饰。如：
This hat is by far / much / nearly / almost / not nearly / by no means / not quite / nothing like the biggest.
How much did the second most expensive hat cost?
③表示“最高程度”的形容词，如excellent、extreme、perfect等，没有最高级，也不能用比较级。
④形容词最高级修饰作表语或介词宾语的名词、代词时，被修饰的词往往省略。如：
He is the tallest(boy)in his class.
⑤作状语的副词最高级前可以不加定冠词。如：
Of all the boys he came(the)earliest.