Using A-share private companies in Shanghai and Shenzhen from 2010 to 2022 as research samples, a panel model was used to examine the impact of state-owned capital participation on the quality of information disclosure of private enterprises, and robustness tests were conducted using methods such as Differences-in-Difference with multiple time periods. Research has found that state-owned capital participation can improve the quality of information disclosure in private enterprises by improving internal control quality, alleviating financing constraints and increasing media attention; At the same time, this promoting effect is more significant in areas with high levels of marketization and private enterprises with more severe agency problems; Further research has found that on the basis of improving the quality of information disclosure in private enterprises, state-owned equity participation would also have a positive impact on investor confidence and corporate value. This study provides empirical evidence for further improving the quality of information disclosure in private enterprises, as well as decision-making references for government macroeconomic regulation and the healthy development of private enterprises.