Studying the reasons for the underinvestment of innovation project is a hot topic in corporate finance.Based on the study and analysis of dynamic models between investors and managers, this paper reveals that managers cut down the investment volume of innovation project under financial constraint condition;agency problem can enlarge the degree of under investment under financial constraint condition.These game results are also proved by examples.What's more, this paper suggests that high disclosure quality, with powerful law protection ,can improve the investment volume of innovation project and hence reduce the degree of underinvestment of it.