The institutional investor network clique formed on the basis of the joint shareholding property right correlation is of great significance for promoting the reasonable control of risk bearing level of enterprises and realizing long-term stable development. Based on the data of A-share listed companies from 2007 to 2022, this paper uses Louvain algorithm to measure the tightness of institutional investor network clique, and explores whether and how institutional investors group behavior in the network affects corporate risk-taking. It is found that the institutional investor network clique has the risk mitigation effect, which can suppress enterprise risk-taking levels through the joint governance effect and the consulting support effect. The heterogeneity analysis shows that the above effects are markedly different in different enterprise characteristics, institutional investor characteristics, and external information environments. The research conclusion provides empirical evidence and situational basis for effectively exerting the governance effect of institutional investor network clique and reducing corporate risk behavior.