The purpose of this study was to the impact of Perfectionism on explanatory style (optimism-pessimism) with the mediating role of exam anxiety in students.  This research is one of the correlation and path analysis methods. The statistical population of this study was all students of the Islamic Azad University of Tehran in 1397-1396, of which 761 were selected as cluster sampling method. The research tools were Sarasson's test anxiety (1984), perfectionism Flett & Hewitt (1991) and the explanatory style Sheer & Carver (1985), all of which are of validity and reliability Acceptable. The AMOS analysis method was used to analyze the data. The results showed that perfectionism has no indirect effect due to test anxiety on explanatory style (optimism-pessimistic). Also the results showed that perfectionism had a direct effect on explicit style (optimism-pessimistic). Also, Perfectionism has a direct effect on test anxiety. In total, the model of the model was acceptable and the corrective model had suitable fit. The results indicated that perfectionism, explanatory style (optimism-pessimism) play an important role in the test anxiety. Therefore, considering these factors in therapeutic and educational interventions to reduce the test anxiety can be very effective.