The purpose of this study is to investigate and test the relationship between the quality of accounting information disclosure and the ownership of institutional investors during the market downturn in the Tehran Stock Exchange (TSE). The method of the present research is applied in terms of purpose, and its research design is semi-experimental using a post-event approach in the period 1394 to 1398. By systematic elimination method, 107 companies (equivalent to 535 years-company) were selected as the research sample. the quality of accounting information disclosure has been determined as an independent variable, institutional investor ownership as a dependent variable, market downturn and financial distress as moderation variables. The research hypotheses were tested using Eviews 10 software and the ordinary least squares (OLS) method. The results showed that the disclosure of quality information in companies increases the presence of institutional investors, in other words, there was a positive and significant relationship between the quality of information disclosure and the ownership of institutional investors. By disclosing quality information, companies have increased the share of institutional ownership even in times of market downturn and financial distress. These results indicate the significant effect of moderating variables on the relationship between the quality of information disclosure and the ownership of institutional investors. Therefore, considering the positive and significant effect of quality information disclosure on increasing the institutional ownership of companies, expanding and promoting the efficient structure of quality information disclosure in companies is recommended to increase the sustainable presence of institutional investors.