Objective To analyze the clinical features and pulmonary radiological findings of primary anti-neutrophil cytoplasmic antibody(ANCA)-associated vasculitis (AAV).Methods Clinical data of 271 ANCA positive primary AAV patients admitted in Shanghai Ruijin Hospital from January 2003 to November 2015 were retrospectively analyzed.Among 271 patients,there were 211 myeloperoxidase (MPO)-ANCA positive cases (MPO subgroup),52 proteinase 3 (PR3)-ANCA positive cases (PR3 subgroup),and 8 dual positive cases (dual subgroup) according to ANCA classification.The demography,clinical characteristics,pulmonary radiological manifestation and renal function were compared among three subgroups.Results MPO subgroup had more renal (x2 =4.968,P =0.026) and constitutional symptoms (x2.=8.901,P =0.003) than PR3 group,while PR3 group had more ENT symptoms (x2 =19.843,P ＜ 0.001),cough (x2 =6.623,P =0.010),hemoptysis (x2 =8.656,P =0.003),dyspnea (x2 =5.127,P =0.024),buccal and ocular mucosal symptoms (x2 =4.818,P =0.028) than MPO group.In lung radiology,interstitial manifestations were displayed more frequently in MPO than PR3 group (x2 =4.237,P =0.040),while pulmonary nodules was more frequent in PR3 than MPO group (x2 =4.503,P =0.034).Dual subgroup tended to have more nervous,respiratory and renal impairment.Renal function showed that MPO subgroup had higher creatinine (Z =-5.529,P ＜ 0.001),urea (Z =-4.646,P ＜ 0.001) and uric acid levels (Z =-2.331,P =0.020) than PR3 subgroup.Dual subgroup had higher creatinine (Z =-3.251,P =0.001) and urea (Z =-2.882,P =0.004) levels than PR3 subgroup,but there was no difference with MPO subgroup.Conclusion There are significant differences in both clinical and pulmonary radiological manifestations between the MPO and PR3-ANCA subgroup of primary AAV.