In this paper, Guile’s and Hayne’s model has been adopted to measure the conservation. Furthermore, we have used Tehran stock exchange ranking system to measure the voluntary disclosure. In this system, the companies that have been ranked are based on their disclosure quality. On the other hand, the size of the company and the debt ratio are used as the control variables. Regarding the theoretical background of our topic, we have used the library sources, books, and articles which were related to our paper To test hypotheses, the data of 97 listed companies at Tehran stock exchange have been used. The data were gathered over a six-year period from 1385 to 1390. Regarding preliminaries data, they have been extracted from the financial statements and their accompanying notes. The method of least square regression and pooled data has been used in order to test these hypotheses. The findings of the study show that there is a negative relationship between the conservatory and voluntary disclosure in the big and small firms. Moreover, the results explain that the relationship between the firm size and the level of voluntary disclosure of information is a positive and a significant relationship. On the other hand, at the making the comparison between the big firms and the small ones, we get a lesser voluntary disclosure.