This paper uses data from the China Education Tracking Survey (CEPS) to explore the impact of peer relationships on the academic performance of students in the ninth grade. First, according to the number of migrants in the area, the sample is divided into three groups, namely, Shanghai, a region with a large number of floating population and a national core sample formed in other parts of the country. Then, the local students in each sample group are grouped with the foreign students, and the impact of peer relationship on their academic performance is analyzed respectively by regression analysis. Then the differences among the groups are compared. Finally, the sample is limited to the sample of students in the rural household registration system. Parent-child relationship is added to control the influence of the family environment and a robustness test is conducted. Through these empirical studies, we find: 1) There are differences in the impact of peer relationships on academic performance in different regions. In the Shanghai sample, there is no significant correlation between peer relationship and academic achievement; in regions with a large number of floating population, the quality of peer impact on academic performance is greater than that of national core sample with fewer floating population. 2) The impact of peer relations on students in different regions in China and foreign countries is different. In areas with a large number of floating population, peer relationships significantly affect the academic performance of overseas students. In the national core sample, peer relationships significantly affect the academic performance of local students, with no significant impact on foreign students. 3) There are differences in the impact of peer relations on Chinese and mathematics. Among them, the least impact on the language proficiency. 4) There is a significant positive correlation between student evaluation of peer relationships and academic achievement. The impact of communication frequency on academic performance may be poor.