Academic achievement is one of the most important indicators for assessing students' performance and educational attainment. Family socioeconomic status (SES) is the main factor influencing academic achievement, but the relation between SES and academic achievement may vary across different sociocultural contexts. China is the most populous developing country with a large number of schooling students in the basic education stage. Chinese schools are unified and managed by the Ministry of Education, but the central and local governments in accordance with their responsibilities share the investment of educational funds. However, the strength of the relation between SES and academic achievement and possible moderators of this relation remain unclear. Therefore, we conducted a meta-analysis on the relation between SES and academic achievement based on 215,649 students from 78 independent samples in the basic education stage from mainland China. The results indicated a moderate relation between SES and academic achievement (r = 0.243) in general. Moderation analyses indicated that the relation between SES and academic achievement gradually decreased in the past several decades; SES has a stronger correlation with language achievement (i.e., Chinese and English) than science/math achievement and general achievement. These findings were discussed from the perspective of governmental policies on education.