This study investigated the relationship between free cash flow and some aspects of corporate governance principles to over investment in companies listed on the Tehran Stock Exchange. Information needed for the study of the financial statements of 81 companies in the period 1390-1394 has been collected. Multivariate regression was used to test the hypotheses with data is consolidated. Findings suggest that between the standards of corporate governance and over-investment there is a significant negative correlation andthe result of these measures are key factors in reducing over investment. Free cash flow and over investment between positive and significant relationship. As a result, free cash flow is a key factor in the creation of over-investment, leading to problems of asymmetric information and agency problems. as well as the standards of corporate governance and over-investment in companies with high free cash flow than firms with low free cash flow there is a significant difference and reduce the impact of over-investment through corporate governance standards in the company much more.