一般用于定语从句中,在定语从句中有区别
all of them 可以作为主语,指所有的XXX,这个them所指的对象前文中已经提到的,可以指人、事物等等,举个简单的例子：We have ten people in the room; all of them are girls.其中all of them are girls也可单独成句.
all of which和all of whom 都只能引导从句,进行补充说明,不可置于句首.但which指事情或者物,whom指人.例句：
1、The vases on display are highly valuable,all of which were made in China.这句也可以拆分成两句The vases on display are highly valuable.All of the vases(them) were made in China.
2、The students are hard-working,all of whom wish to enter top universities.这句可拆分为The students are hard-working.All of the students(them) wish to enter top universities