Default risk is the composite result of other risks faced by companies,posing a significant threat to their normal operation.Common ownership adopt strong incentive measures over regular institutional investors in regulating the companies and reducing the default risk of the companies where they hold share.Using A-share listed companies from 2012 to 2022 as a sample this study shows that common ownership can significantly reduce the default risk of companies.The use of a difference-in-differences model to alleviate potential endogeneity problems also supports the conclusion that common ownership can significantly reduce the default risk of companies.Further analysis reveals that the impact of common ownership on companies'default risk is greater when the liquidity of their stocks is lower,the number of companies where they hold shares is higher in specific industries,and the product market competitive advantage is lower.The research conclusions have implications for the micro-foundations of achieving high-quality economic development.