With the launch of a new phase of Chinese-style modernization, promoting the high-quality development of social organizations has become an essential requirement for deepening social governance, enhancing public services, and improving social welfare. Based on panel data from 1,958 observations of 414 foundations across China from 2012 to 2021, this study empirically analyzes the impact of government funding on the high-quality development of social organizations. It further explores the mediating effect of mission drift and the heterogeneous influences of institutional environments and political attributes. The study finds that: (1) Government funding significantly promotes the high-quality development of social organizations; (2) Mechanism analysis reveals that government funding induces mission drift, which drives strategic adjustments in social organizations, thereby advancing their high-quality development; (3) Heterogeneity analysis reveals that the institutional environment has no significant impact on the effect of government funding; meanwhile, social organizations with governmental backgrounds exhibit better development performance when the funding dependency is higher, indicating that political attributes strengthen the effect of funding through the dependency pathway. This research not only deepens theoretical understanding of government-society relations but also provides practical policy references for fostering the high-quality development of social organizations.