Since reporting and determining organization and business entities’ profit has been placed in accounting’s expert’s circle of attention, quality of earning is considered as one of the most important theoretical areas and always stressed on its importance. Although goal of this research is to find effective factors regarding quality of active companies in Iranian capital market, but lack of a comprehensive measure for earning quality and precise statistical based criteria has been proofed which is considered as the main problem in pas research in this field. We addressed this problem in our article. Also across all the pas researches in Iran, none of them could represent a comparative analysis of Iranian companies’ earning quality with other countries. Using a comprehensive earning quality measurement is on the most advantages of this article from the pas ones. We measured quality of earning by using seven indictors (relativity, accrual quality, timeliness, conservatively, smoothing, stability and predictability). Our independent variables in level of companies are: size, sale, sales volatility, cash flow volatility, and loss incurring frequency and investment opportunities). Time period of this research is 2001-2012. Our results imply positive relationship between earning quality and Iranian companies’ size, investment opportunities, also we observed a reverse relationship between earning quality and cash flow volatility. Finally we concluded that in our researching time period cash flow volatility has stronger effect in Iran than other countries.