1. 两者都表示“许多”，但 many 修饰或代替可数名词(复数)，与 few(少数)相对;而 much 用来修饰或代替不可数名词(单数)，与little(少量)相对。
例句：Did you see many people there?
你在那儿看见许多人了吗?
Do you have much money left?
你剩的钱多吗?
2. 关于many of 和 much of：
①其后接名词时，该名词通常应是特指的(比如有the, these, those, my, our, Tom's等修饰)。
例句：Many of the farmers grow rice.
很多农民种稻子。
He spends much of his time outdoors.
他很多时间都在户外度过。
②如果名词没有表特指的限定词，通常就不用of。Many和Much的用法区别。
例句：误：She didn't eat much of breakfast.
正：She didn't eat much breakfast.
她没有吃多少早餐。
③如果用了介词of又没有特指限定词，通常是不可以的。
例句：误：Many of students have read it.
正：Many of the students have read it.
许多学生读过它。
④在少数情况下，much of之后不跟限定词也可以用，这主要见后接人名和地名的情形。
例句：I've seen too much of Howard recently.
最近我见霍华德见得太多了。
⑤在人称代词前总是用many of或much of，其中的of不能没有。
例句：I didn't eat much of it.
这个我没吃多少。
⑥much of有时可用于一个还有不定冠词的名词前。
例句：You can’t see much of a country in a week.
一周之内看一个国家看不了多少地方。
not much of a 有时可用于名词前表示某人对某物或某人评价不高。
例句：That might not seem like much of an accomplishment.
那似乎算不上什么成就。
3. 两者都可与 more 连用，其区别仍然是 many more之后接复数名词，much more 之后接不可数名词。
例句：There have been many more burglaries this year.
今年盗窃案比过去多好些。
4. 注意“many a+单数可数名词”的用法：形式上为单数，但意义上为复数(意为“许多”)，若用作主语，其谓语通常与形式一致而不与意义一致(即谓语用单数)。
例句：I have told him many a time to be polite.
我多次告诉他要有礼貌。
