Accounting restatement has become an increasingly common phenomenon in financial reporting. Restatements clearly signal that the firmۥs prior financial statements are not credible and are of relatively lower quality. A restatement can cause investors to reevaluate their expectation for future prospects of the firm, either because amended historical results trigger a restatement of expected future cash flows or because the restatement calls the credibility of management into question. Test had been accepted from the 185 companies in Tehran Stock Exchange during the recent ten years the indicated results consistent with the existing theory. There is a long-term decrease in the information content of earnings following earnings restatements.