Abstract: Due to the agency costs associated with external equity, although reverse mixed-ownership reform can bring more development opportunities, it also suppresses their commercial credit financing behavior. Using a sample of A-share listed companies from 2003 to 2023, this paper empirically examines the impact of reverse mixed-ownership reform on the commercial credit financing behavior of private enterprises and its underlying mechanisms. The study finds that reverse mixed-ownership reform significantly reduces the commercial credit financing activities of private enterprises. This effect is more pronounced when private enterprises are located in regions with lower marketization, have higher internal control quality, and have not received non-standard audit opinions. The conclusions remain robust after addressing potential endogeneity issues. Mechanism analysis reveals that reverse mixed-ownership reform reduces commercial credit financing by increasing the agency costs of external shareholders. This research extends the study of the economic consequences of reverse mixed-ownership reform, largely supports the theory of commercial credit financing as an alternative financing source, and provides insights for the government in promoting reverse mixed-ownership reform and for private enterprises in improving financing efficiency.