Abstract: "Institutional Shareholder Activism"has become an important feature in Western securities market.According to economy game,the condition of institutional investor actively participating in corporate governance is analyzed in this paper.It shows that the motive force of institutional investor actively participating in corporate governance depends on the comparison of costs and revenues,to be more specific,on the proportion of shares,the length of share-holding and supervising costs,etc.Meanwhile,suggestions are proposed based on the result of game analysis on how to raise the motive force of China's institutional investor actively participating in corporate governance.