This is more difficult. At present, the doctoral supervisor of Yanshan University is only allowed to bring one doctor. If you are on the job, you can't give him a job, and he is less likely to want you. However, there is still hope. Now Yanshan University has approved another batch of doctors this year, which is not very famous. You can think about it. It should be promising. Then there is the exam you mentioned, which is not a problem. Specialized courses and so on, as long as the teacher agrees, you can take the doctor's exam. .

You'd better contact the teacher early. As long as the teacher decides to take you, you have an 80% chance to study for his PhD, and the other 20% is the exam.