The purpose of this research is to explain the conservatism pattern and prioritize the effective factors in companies admitted to the Tehran Stock Exchange. The information necessary for this research was compiled from financial statements of 154 companies. To test the hypotheses, multiple regression has been used with panel data. In line with the research objectives, conservative variables were calculated using Givoly and Hein (2000). Effective factors on conservatism were identified and selected by referring to previous studies and using theoretical foundations. The results of the research show that the criteria of free cash flow, financial leverage, earnings management, cost of capital, board of independence, over confidence management, CEO compensation, size and disclosure quality in the order of priority of factors influencing the criterion accounting conservatism. In other words, corporate characteristics and managerial thinking are more influential than other factors in the practices adopted in the company. The results also confirm that conservatism is related to contract theory.