With the improvement of ESG awareness and the increasing importance of sustainable development, ESG rating has become a focal point of discussion in both academic and practical fields. However, at present, the ESG rating standards in China are not unified, and there is significant divergence in the scores given by different rating agencies. Will this have an impact on business risk? Based on this, using Chinese A-share listed companies from 2015 to 2022 as the research sample, the ESG rating divergence index was constructed using the ratings of Huazheng, Wind, FTSE Russell, SynTao Green Finance, SusallWave and Bloomberg, and the impact of ESG rating divergence on business risk was empirically tested. It is found that ESG rating differences significantly increase the business risk of enterprises, and this conclusion is still valid after a series of endogenous robustness tests. The mechanism test finds that ESG rating divergence increases business risks by aggravating information asymmetry and inhibiting investor sentiment. Heterogeneity analysis shows that the impact of ESG rating divergence on business risk is stronger in non-state-owned enterprises, enterprises with poor information quality and highly marketized enterprises. Further research finds that compared with the differences in the analysis of ESG rating agencies, the non-standard disclosure of ESG information by the rated enterprises themselves is the main reason why the ESG rating divergence aggravates the business risk of the enterprises. The research conclusions provide an important reference for regulators to standardize ESG rating standards to guide enterprises in disclosing information properly, which provides an important reference for promoting the construction of China's ESG rating system.