Whom can be used instead of who when it is the object of a verb or preposition. It can be used in the following ways: 作动词或介词的宾语时，who可以用whom来替换。whom 有以下用法

as a relative pronoun (referring back to a person and starting a relative clause): 用作关系代词（回指人并引导关系从句）: Students for whom English is a second language should consider taking the course. 以英语作为第二语言的学生应该考虑上这门课。 The book was written by his wife, Joan, whom he married in 1962. 这本书是由他的妻子琼写的，他与她在1962年结婚。 (starting a relative clause that is the subject, object, or complement of another clause): 引导作另一分句的主语、宾语或补语的关系从句: I don't know whom you've already met. 我不知道你已经碰见过谁。

as a question pronoun: 用作疑问代词: Whom do you blame? 你怪谁呢？

Whom is only used in written English and in formal spoken English. Who is normally used as the object of a verb or preposition, but immediately after a preposition whom is generally used: whom 只用于书面语和正式口语中。who 常用作动词或介词的宾语，但紧接在介词后时一般用whom: the man with whom she lived. 跟她同住的那个男人。 It would, however, be more natural to say: 但常常这样说更自然: the man she lived with 跟她同住的那个男人。.