Abstract: This study analyses all A-share listed companies from 2015 to 2020 to empirically examine the impact of inquiry supervision on corporate value and the moderating influence of corporate social responsibility (CSR) on this relationship. Research has shown that inquiry supervision significantly reduces corporate value, and the corporate social responsibility previously performed by companies can weaken this negative impact. Furthermore, the heterogeneity test based on internal and external controls shows that the reputation protection effect of CSR is more significant for companies with a higher proportion of independent directors, companies with a higher proportion of institutional investors investing in stocks, regions with a higher degree of marketization, and regions with a higher level of rule of law. The research in this article validates the effectiveness of reputation protection and verifies that reputation protection, as an informal mechanism, is easier to fulfil a role in areas where formal mechanisms are perfect. In other words, formal and informal mechanisms appear to complement each other. These findings provide empirical insights into the governance of CSR.