Abstract: This paper studies the relationship between overconfidence of managers, financial flexibility of enterprises and overinvestment, and selects the data of listed companies from 2005 to 2016 as samples for empirical research.The results show that overconfident managers can further promote overinvestment behavior by holding a higher level of cash flexibility.At the same time, overconfident managers tend to hold higher liabilities, which will increase the over-investment behavior of enterprises by reducing their debt flexibility.