What should be done about a professor who treats foreign students worse than domestic students?

Your university almost certainly has an office devoted to considering situations of racial harassment and discrimination. If the behavior is in general towards international students rather than just Chinese ones, this is usually also explicitly prohibited as "national origin" rather than race. You should Google your university name along with the phrases "civil rights office" or "discrimination." Usually you can make a report to them, often anonymously, and in theory you ought to be protected from retaliation.

Note that from what you've said here, I would be surprised if serious action was taken against the professor -- his actions were bad but no single action crosses the line, you say, and behavior like this is sadly common. However, it may result in a reprimand (which can, after all, change behavior if he feels pressured). In addition, I would encourage you to make this report so that, if his behavior ever escalates, there will be a case history. So often I read stories about harassment cases in academia where the defense is something like "well this was just one offense" and it seems it almost never is in reality; just the first one reported. If you say something, then the next person who says something (and may have a more serious complaint) is more likely to be believed.

Most universities provide anonymous teaching evaluations for professors at the end of the course -- that is, the students are given forms to evaluate the course, the teaching, etc. In my experience, these forms are taken very seriously by the various Deans offices. It's expected that there will be a certain level of disgruntled complaining, but if multiple people in the same course complain about race-based harassment, it's likely to get a response; whether a serious talk with the professor, or removing him from teaching duties.