Based on the data of Shanghai and Shenzhen A-share listed companies from 2018 to 2023, this paper empirically examines the impact of ESG performance on financial reporting comparability and its mechanism. The research findings are as follows：The better the ESG performance, the higher the financial reporting comparability, but ESG rating divergence will weaken the impact of ESG performance on the financial reporting comparability. The mechanism test shows that ESG performance promotes the comparability of financial reports by restraining the manipulation of accounting methods. The heterogeneity test reveals that in enterprises with weak internal control and low level of external audit, the role of ESG performance in enhancing financial reporting comparability is more significant. Further research indicates that the comparability of financial reports determined by ESG performance can significantly reduce the debt capital cost of enterprises. The research results provide a theoretical basis for government and enterprises to attach importance to ESG performance and help stakeholders evaluate the quality of financial reports.