How to renew my child"s expired passport?

Dahong, first if all, please get all the required documents ready, including:
1. A truly filled-out application form;
2. Four full-face 48mmx33mm size color bare-headed photos;
3. The original and photocopy of your son's passport;
4. The orginal and photocopy of his US residence card;
5. His personal statement.

Then go to the embassy to submit the application.

Note: If your son is not elder than 16, your wife and you should go together with your son to the embassy and submit relevant materials (his birth certificate, parents' pasports and residence cards, etc.). In case that one of the parents can't be present at the embassy, he or she should provide an authorization letter proving the consent for the issuance of new passport to the son.