When it comes to homophones, or words that sound the same but are spelled differently, it can be rather difficult to tell the two words apart. When do you use which word? This post explains the difference between who’s and whose.

Who's v. Whose
Both these words deal with people. The difference is what situations they show.

Who's is the contraction for who and is.
Who's 是who和is的缩写

Every time you use this word, you must be asking or talking about someone. You should be able to substitute who is to any use of who's. If the sentence still makes sense, then you have used it correctly!
每次使用这个词的时候一定是在询问或谈论某人。Who's的使用方法与who is相同。如果替换这两个词后句意不变,那么你使用的就是正确的!

Most commonly, who's is used to ask a question. Note that using a contraction is usually standard in English speaking, but is not formal enough to use in a written piece.

Who's the person in charge of organizing the food and drinks for this party?

Who's knocking at the door?

Likewise, you can use it in statements.

I have a friend who's interested in the open position at your company.

I can't believe who's walking around the neighborhood this late at night.

Whose is used to show possession.

The list of equivalent words for whose includes my, his, her, our, your, etc. If you are asking whether something belongs to someone, you can use whose. Substituting any of the possessive pronouns for whose should make for a sentence that makes sense.
whose可以用来表示包括my, his, her, our, your等词所表示的一些所属关系。如果询问某样东西是否属于某人,可使用whose。可用相应所有格代词代替用由whose组成的句子。

Whose books are these that have been left all over the floor?

I do not know whose trash that is, but it has been there for the past week.

In addition, whose can be a transition word to join an adjective phrase to a person or group of people. Whose and that both serve this purpose, and you use whose when the adjective is talking about a subject that is a person.

I just met a man whose daughter is studying for her college entrance exams, just like I am!

The student whose parents do not have enough time to care for him or her is likely to do poorly in school, even if the family is of high socioeconomic status and hires tutors for the child.