The purpose of this study is to investigate the effects of the regulatory ownership on conservatism of accounting firms in Tehran Stock Exchange. In doing so, data from 121 companies listed in Tehran Stock Exchange from 1385 to 1390 were used. And using a panel analysis method alongside Eviews software, research hypotheses were investigated. To measure conservatism, two models of Shiva Kumar and Basu Ball have been used. The results showed that there is a negative and significant relationship between regulatory ownership, conservatism of firms accounting sector. This means by increasing regulatory use of conservative methods in economic units will decrease.