As the global ecological and environmental problems become more and more serious, the concept of green finance and sustainable development has been advocated by more and more domestic and foreign experts, scholars and investors, and the Environmental Responsibility, Social Responsibility, and Corporate Governance (ESG) rating has gradually become a hotspot of attention. ESG is a kind of investment concept and a comprehensive assessment criterion of corporate performance for systematic evaluation of enterprises, and it has become an important indicator of the ability of measuring the sustainable development of enterprises. It has become an important indicator of corporate sustainable development capability. In this paper, we investigate the relationship between ESG ratings and cumulative abnormal returns of listed companies’ stocks under the impact of sudden risk events. The outbreak of the New Crown epidemic as an exogenous risk event provides an opportunity for this paper. This paper examines the role of firms’ ESG ratings and the three sub-dimensions of ratings on the cumulative abnormal returns of listed firms’ stocks during the New Crown Epidemic outbreak and verifies the role of ESG ratings on firms in times of crisis. The final regression results prove that under the impact of sudden exogenous risk events, listed firms’ ESG ratings have a positive effect on the cumulative abnormal stock returns during the event window. Finally, this paper provides recommendations to help firms and investors prevent and mitigate risks.