The purpose of this study, is the study of influence of conservatism on relationship between operational cash flow and income taxed definitively accepted by the companies on the Tehran stock exchange. This research in terms of the objective applied research and in terms of the type of the exercise method, is a description- correlation and the type of solidarity – data, a little bit. In this research to collect data related to the research’s variables the audited financial statement has been used. The statistical community this research accepted all the companies on the Tehran stock exchange and to determine the samples of systematic removal method (388). For data analysis and correlation coefficients of test hypotheses, t statistics and regression by SPSS is used. finding, show the significant relationship between operational cash flow and definitive taxable income, and conservatism imoact on the relationship between operational cash flow and definitive taxable income.