Peking University, Nankai University and Shanda University are all good. I'm from Shandong University, and our math is the sixth in China. The College of Mathematics consists of four departments: Mathematics and Applied Mathematics, Information and Computational Science, Statistics and Information Security, and seven research institutes: Basic Mathematics, Scientific Computing and Software, Applied Mathematics, Systems and Operations Research, Control and System Science, Probability Theory and Mathematical Statistics, and Information Security. System science and operational research are very distinctive. In addition, Academician Peng Shige has set a world precedent for financial mathematics, and will give an hour-long lecture at the next World Congress of Mathematicians, which is a privilege only for top scientists in the world. Mathematics is a characteristic subject of Shanda University. You can look at the website of Shanda Institute of Mathematics, which contains detailed subject introduction and tutor introduction, hoping to help you. I don't know which school you went to as an undergraduate, but at least I don't think Laishan University will treat you badly in mathematics.