["Asian-Pacific Economic Literature, Volume 39, Issue 2, Page 61-73, November 2025. ", "\nABSTRACT\nPromoting the transformation of the state‐owned assets supervision system (SASS) from ‘managing assets’ to ‘managing capital’ is the key direction of the new round of state‐owned assets reform. This article takes the policy implementation of state‐owned capital investment and operation companies (‘two types of companies’) as a quasi‐natural experiment, selects Chinese A‐share listed state‐owned enterprises (SOEs) from 2009 to 2022 as the research sample, and investigates the impact of SASS reform on the performance of SOEs using a multi‐period difference‐in‐differences model. The results suggest that SASS reform can significantly improve the performance of SOEs. Mechanism analysis indicates that SASS reform enhances the performance of SOEs by weakening government intervention, increasing external pay gaps, and reducing agency costs. Heterogeneity analysis shows that SASS reform on the performance of SOEs is affected by the administrative levels, industry attributes, and external institutional environments. The performance‐enhancing effect of SASS reform is more significant in central SOEs, competitive SOEs, and SOEs with a better external institutional environment. The findings enrich the research on the economic consequences of SASS reform and the factors affecting the performance of SOEs, providing empirical evidence for deepening the reform of state‐owned capital and SOEs and promoting the high‐quality development of SOEs.\n"]