The many social and economic costs that bankrupt companies impose on their shareholders have motivated researchers to provide several studies to pay attention to bankruptcy. The purpose of this research is to investigate The effect of ownership concentration on the relationship between auditor's abnormal fee and bankruptcy risk. Research in terms of purpose is part of applied research and research method in terms of nature and content is cause and effect. The research was conducted in the framework of deductive-inductive reasoning and panel analysis was used to analyze the hypotheses. The statistical population of the research was all the companies admitted to the Tehran Stock Exchange and using the systematic elimination sampling method, 150 companies were selected as the research sample in The 9-year period between 2013 and 2021 was investigated. The results of the research hypotheses test showed that There is an inverse relationship between auditor's abnormal fee and bankruptcy risk; But this relationship is not significant; Also, ownership concentration has an effect on the relationship between the auditor's abnormal fee and bankruptcy risk and strengthens this inverse relationship.