Generally speaking, mathematical analysis and advanced algebra must be tested, but I don't know what else will be tested in the second interview. Complex variable ordinary differential equations are all possible. There are many courses in the department of mathematics, which are also very difficult. Self-study is really not easy. You can also consult the seniors/seniors and teachers of the department of mathematics in your school and give good advice.

In the aspect of mathematical analysis, I recommend the Course of Mathematical Analysis by Professor Shi Jihuai and Professor Chang Gengzhe of the Chinese University of Science and Technology and the Guide to Solving Problems in Mathematical Analysis by Professor Peking University Qu. Advanced Algebra recommended Professor Qiu published by Tsinghua University Press and Professor Xu published by Tsinghua University. If you can finish these studies, it will certainly be of great benefit to you. There are still many good books, of course, you can also buy the two sets of problem sets mentioned above. )

In addition, it should be very, very difficult for liberal arts students to test basic mathematics, but it is not impossible.

Practice the questions of previous years.

The political score in English can't be low.

Finally, learn advanced courses, functionals, algebra, topology and so on.