Based on agency theory, housekeeping theory and socio emotional wealth theory, this paper analyses the influence mechanism of the informal governance mechanism of family management on auditors risk decision making behavior, and uses the sample of A share listed family enterprises from 2013 to 2017 to carry out an empirical test. The empirical results suggest that family management can affect auditors risk decision making behavior, which is manifested in the significant reduction of audit fees and the probability of being issued non standard audit opinions. The closer the family business executives are to the actual controller, the lower are the audit fees and the probability of being issued non standard audit opinions. Agency Costs I plays a mediating role between family management and family members’ kinships and auditors’ risk decision making. When the degree of separation between ownership and control is relatively low, the effect of family management on audit fees and the probability of being issued non standard audit opinions is more significant. From the perspective of enterprise life cycle, the influence of family management on auditors risk decision making is not significant in the recession period. This paper analyses the characteristics of audit risk of family business, which is helpful to the choice of governance system of family business and the response of auditors to governance risk of family business.