My appearance patent application was before his utility model patent application (the products are very consistent), and the appearance changed slightly. Can I invalidate him with my patent?

Whether it is invalid or not, you need to compare your patent authorization text with the authorization text of the utility model patent application, and then you can draw a basically accurate conclusion!

The invalid process has no effect on your application, but if you lose, you will lose financially, because all the expenses of the invalid process need to be paid out of your own pocket, hehe.

I suggest you find a formal organization that has done successful and ineffective cases to help you analyze them.

But I remind you: because the process of patent invalidation is a legal process, which requires evidence and rigorous analysis, any formal agency will charge you for issuing a report and concluding comments on whether the other party's patent can be invalidated.