Objective　To investigate clinical features, immunologic and genetic characteristics of COPA syndrome. Method　Characteristics of clinical materials, immunological data and gene mutation of the first case in China with COPα gene mutation were retrospectively analyzed. Result　A 10-year-3-month old girl was admitted due to mental deterioration for half a month and edema for six days. She looked a little pale. The blood pressure was 170/98 mmHg. There were scattered bluish purple ecchymosis in her extremities and obvious edema in her face and lower limbs. Abdominal distension and positive mobile dullness were found. Urinary analysis revealed of positive urine protein and red blood cells. Rheumatoid factor, antinuclear antibody and anti-double-stranded DNA antibody were positive. Anti-Sm antibody was negative. CT images showed lesions of left lower lung lobe and a small amount of pleural and pericardial effusion. MRI revealed of effusion and partial synovial thickening of left ankle and foot joints. Renal pathology showed moderate-to-severe diffuse hyperplasia of glomerular mesangial cells with endothelial cell hyperplasia. IgG deposited at glomus, capillary loops, and mesangial area. The gene sequencing results showed COPα gene c.433C>T,p.P145S heterozygous mutation. Flow cytometry detection deployed a significantly increased Th17 cell ratio (6.3%). Conclusions　The main clinical features of COPA syndrome include lung lesions, arthritis, renal damage and positive autoantibodies . Th17 cell ratio is significantly increased. Gene sequencing analysis shows pathogenic variation of COPα gene.