Abstract This study investigation the Effect of Using Fair value in Financial Reports in Improving the Value relevance of Accounting Information. The ultimate goal of this study is to determine the difference of the value relevance of accounting information between the fair value system user’ companies and the historical cost user' one.This research from an objective point is an "applied", from the executive aspect is a "descriptive-correlation", and from the essence perspective is a "post events and quantitative". This research has taken place on the statistic samples of the 95 listed companies in the Tehran Stock Exchange during the years of 1387-1393. After collecting data and calculation of the basic variables, all of the hypotheses of research were tested by the using of data panel model. For to investigate the relationship between the variables have been used of simple and multiple linear regressions. The results of this research show, the value relevance of Earnings Per Share, and the value relevance at the same time of Earnings Per Share and the Book value, in the companies which have used the Fair value method is more than the companies which have used the Historical cost system.