The quality of financial reporting is an important criterion in the correct decision of investors, and shareholders rely on financial reports to invest more or sell their shares. Numerous factors can improve financial reporting. One of these factors is the expertise of the auditing industry. In the present study, the effect of auditor's expertise in industry on the quality of financial reporting of companies listed on the Tehran Stock Exchange is examined. This research is applied in terms of purpose and in terms of methodology, correlation is a type of causal (post-event) research. The statistical population of the study was all companies listed on the Tehran Stock Exchange. 127 companies of Sanat Khodro Company were selected as the research sample and were surveyed for a period of 6 years between 1392 and 1397. The method used to collect information is library and multiple linear regression has been used to test the hypotheses. Stata version 15 software was used to run the tests and estimate the models. The results of the study show that the auditor's expertise in the industry has a positive and significant effect on the quality of financial reporting. In other words, in companies whose audits are performed by industry-specific auditors, the quality of reporting is much higher than in other companies.