Based on the exogenous shock of the 2008 Corporate Social Responsibility (CSR) Mandatory Disclosure Policy, this article uses the hand-collected data of corporate green patent and the PSM-DID method to examine the impact of mandatory CSR disclosure on corporate green transformation from the perspective of green innovation. The study shows that mandatory CSR disclosure drives corporate green transformation by strengthening the regulatory legitimacy and normative legitimacy of companies, and this driving effect is more obvious in non-state-owned enterprises, companies with better information environments, and low concentration markets. Further research shows that mandatory CSR disclosure could improve corporate performance through green transformation. This conclusion validates the effectiveness of mandatory CSR disclosure in driving green transformation, deepens and enriches relevant theories of mandatory CSR disclosure, and has a guiding significance for optimizing corporate environmental governance decisions and driving national green economic development.