The ESG behavior of enterprises has already become one of the most important standards for measuring the quality of enterprise development in recent society. Based on the exogenous event of MSCI issuing ESG ratings for enterprises, this article examines the impact of MSCI concern on the disclosure of key audit matters. The research indicates that MSCI concern would reduce auditors’ disclosure of key audit matters, and the lower the ESG rating, the greater the impact of MSCI concern on disclosure of key audit matters. This result indicates that MSCI concern can have a supervisory substitution effect. Mechanism testing shows that analyst tracking and media attention are the two paths through which MSCI concern affect the disclosure of key audit matters. Cross section inspection found that for private enterprises and enterprises audited by non top ten accounting firms, MSCI concern is more effective in reducing disclosure of key audit matters. This article enriches the relevant literature on the economic consequences of ESG rating and the factors influencing the disclosure of key audit matters, and also provides certain policy insights for government departments to further improve the enterprise ESG performance evaluation system and related information disclosure system.