The purpose of the research Decline of Auditors' Financial Bias in Decision making by Professionalism in Auditing: Rough Set Analysis. The research approach is of inductive-deductive type in terms of the data collection meth-od, because it was first determined based on the content analysis of the com-ponents and propositions related to the professional characteristics, then it was tried to confirm or delete the propositions based on the Delphi analysis. This research by participating 14 individuals of the audit partners with the academic degrees over a one-year period, 2018-2019. The results According to the formation of decision making matrix, the results showed that both propositions, the perceptual error of failure to separate the context from con-tent as the Halo bias and the perceptual error of the experience of fraud de-tection in the financial statement as memory bias were determined as the most influential perceptual errors in the audit profession in Iran. In addition, according to gray vikor theory analysis, it was found that the component of the audit's professional maturity was selected as the most important priority and the most effective feature for reducing the audit perceptual bias.
