The objective of this research is to study the relationship between corporate debt financing and earnings quality and also to find the dominance of positive influence of debt or negative influence of debt on earnings quality. The research data were collected from 81 firms listed in Tehran Stock Exchange (TSE), during the years 2005-2009. For testing the hypotheses, multiple regression analysis was used. The results show that there is a negative and meaningful relationship between debt and earnings quality. Also with respect to introduction, in low level of debt, positive influence of debt dominant to negative influence of debt, then the results show that there is a positive and meaningful relation between debt and earnings quality in the firm With low debt. Moreover, with respect to introduction, in high level of debt, negative influence of debt dominant to positive influence of debt, then the results show, there is a negative and meaningful relation between debt and earnings quality.