The mixed-ownership reform has been the mainstream for the SOE reform in China, but rarely is known whether this reform can improve the overall profitability of SOEs. Therefore, this paper would like to fill this literature gap by testing the impact of China's ongoing mixed-ownership reform on SOEs profitability.This reform encourages private capital to purchase shares of SOEs, so it can be regarded as a privatization plan for SOEs. Using the Difference-in-Differences (DiD) approach, we treat SOEs undergoing the reform as the treatment group and those not undergoing the reform as the control group. Our results indicate that the reform significantly increases the profitability of reformed SOEs. Mechanism analysis suggests that the reform enhances SOE profitability by reducing redundant workers, administrative fees, and related-party transactions. We also find that the effects of the reform are heterogeneous, with greater impacts observed among SOEs in unregulated industries, local SOEs, and SOEs in areas with low marketization. Overall, our research enriches the literature on privatization and mixed-ownership reform, and also provides empirical evidence to promote mixed-ownership reform.