Based on the investment efficiency, this paper examines the impact of the external governance mechanism of non-controlling shareholders' network power on corporate behavior. It is found that:the influence of non-controlling shareholders' network power is mainly reflected in governance. And after distinguishing underinvestment and overinvestment, it is found that non-controlling shareholders with high network power both help alleviate the company's underinvestment and restrain overinvestment. The examination of the influence mechanism shows that network power mainly promotes the investment efficiency by inhibiting the tunneling of controlling shareholders, overinvestment of managers and controlling investment chance. When the risk of corporate equity financing is high, and the information and legal environment is poor, network power has a more prominent governance effect on corporate investment behavior.