We are the same major, if we don't cross majors, then most colleges and universities are students of basic mathematics in the five directions of first-level mathematics, and the relative competition is relatively small; Applied mathematics and probability direction are usually the two most competitive directions for mathematics postgraduate entrance examination. I know that the second interview is 2:1; There are not many universities specializing in operational research. You can also consider computational mathematics, if you are interested in things that are partial to computers, such as algorithms.

What direction to study depends on your interest, but the competition of each major in each university is different. The first-level disciplines of mathematics are Peking University, Fudan University, China University of Science and Technology, Nankai University and other universities. There are more 985' s with one or two strong directions, such as the basic mathematics of Wuhan University, Nanda University and Sichuan University, the applied mathematics of Zhejiang University and other universities, the probability direction of Central South University, and the operational research of Zhejiang University and Shandong University. You can consider going to a university with a strong direction.

Moreover, the requirements for the initial examination of each university are not the same. Most universities take mathematical analysis and advanced algebra first, such as Zhejiang University and Wuhan University. However, some colleges and universities have to take several courses, ranging from three to five, and may take complex variable functions, ordinary differential equations and so on. You must find out before taking the exam.

If you have confidence in your professional courses, I suggest you apply for applied mathematics or probability direction, and your employment is relatively better.

good luck