OBJECTIVE To study the clinical characteristics of leflunomide-induced int erstitial pneumonia （Lef-IP），and to provide reference for its clinical diagnosis ，treatment and prevention. METHODS Lef-IP cases published in domestic and foreign journals from January 2004 to June 2021 were collected. Relevant information of patients were extracted and analyzed retrospectively， including basic characteristics ，clinical manifestations ，imaging manifestations ，laboratory examinations ， histopathological examinations ，treatment and outcome. RESULTS A total of 54 Lef-IP patients from case reports of 24 publications were included ，with a median age of 61 years（9-83 years）. Pulmonary symptoms appeared from 3.3 weeks to 132.9 weeks（median time of 14.5 weeks）. Patients with a loading dose of leflunomide have a shorter median time to pulmonary symptoms appearing （7.5 weeks）. The main clinical manifestations were dyspnea （85.2％），cough（57.4％），fever（53.7％）. CT imaging examination showed 19 cases with ground-glass shadow in both lungs ，and 29 cases showed interstitial infiltration in both lungs on chest radiograph；blood gas analysis showed hypoxemia and hypocapnia ；the levels of C-reactive protein and Krebs von Den lungen- 6 （KL-6）increased；histopathological examination mainly showed interstitial pneumonia （8 cases），including 3 cases of diffuse alveolar injury ，4 cases of lymphocytes in bronchoalveolar lavage fluid ，and 1 case of noncaseating granuloma. After discontinued leflunomide and symptomatic treatment （antibiotics，hormones，colecenamine，plasma exchange ），35 patients（64.8％）recovered or improved their lung symptoms. Twelve patients （22.2％）died，and patients with fever may had a higher mortality rate （34.5％， P＝0.02）. CONCLUSIONS The main clinical manifestations of Lef-IP are dyspnea ，cough and fever. Loading doses of leflunomide should be avoided at the beginning of treatment. When lef-IP occurs ，leflunomide is discontinued and corresponding treatment is given，and most of the patients ’pulmonary symptoms can return to normal or be improved.