In recent years， institutional investors in the securities market have played an increasingly important role. They may form cliques through common shareholding relationships and take concerted action. Based on the data of A-share listed companies in China from 2010 to 2020， an institutional investor clique was constructed to explore the impact of cliques stockholding on corporate ESG performance， combining social network theory and agency theory. The research findings show that cliques shareholding effectively enhances the ESG performance of enterprises， i.e.， the greater the proportion of cliques shareholding， the better the ESG performance of the enterprise； cliques shareholding alleviates two types of agency issues by improving information transparency and restraining the self-interest of large shareholders， thus promoting the ESG performance of enterprises； after addressing endogeneity issues and conducting robustness tests， the conclusion that cliques shareholding enhances the ESG performance of enterprises remains valid. The results of further research indicate that the characteristics of cliques affect the ESG performance of enterprises. Specifically， a greater number of cliques， larger scale， richer backgrounds， more stable holdings， and stronger relative power are associated with better ESG performance of enterprises. The research findings not only enrich the study of the consequences of institutional investors’ cliques and the influencing factors of ESG performance of enterprises， but also provide practical insights for listed companies， institutional investors， and the governments.