The purpose of this article is to investigate the effect of overvalued equity on the relationship between audit quality and earning quality. In this article audit firm size, auditor industry specialization and auditor tenure were used as audit quality variable. The sample population consists of 189 companies listed in Tehran stock Exchange during the period 2008 to 2012. To test the hypotheses, OLS in Eviews has been used and investigation method of data is panel. The results show a reverse relationship between all audit quality variables and absolute discretionary accruals indicating that high audit quality causes higher earning quality. But the existence of overvalued equity cause decreasing or reversing of these relationships, in other words, when a firm is highly valued the accruals' decreasing effect of high quality auditors is reduced.