The pathogenesis of IgA nephropathy is not fully understood. In recent years, the complement system has been paid more and more attention in the development of IgA nephropathy, in which the macromolecular protein complement C3 plays a particularly important role. The purpose of this study was to investigate genotype distribution and its correlation with clinical features in patients with IgA nephropathy, with special attention to the role of complement C3. A group of patients diagnosed with IgA nephropathy were selected for the study and clinical data, including medical history and laboratory results, were collected. The genotypic distribution of 8 SNPS (including rs2228570) associated with complement C3 was detected by SNP genotyping. Statistical analysis was also used to evaluate the correlation between different genotypes and clinical features. The results showed that there were significant differences in the genotype distribution of the 8 SNPS in IgA nephropathy patients, and the genotype of rs2228570 was higher in patients. Scatterplot analysis revealed an association between rs2228570 genotype and clinical features, especially renal immunofluorescence markers. Patients with different genotypes showed significant differences in renal function, proteinuria and other clinical manifestations, suggesting that complement C3 may play an important role in the pathological process of IgA nephropathy. This study showed that there was a significant correlation between macromolecular protein complement C3 and genotype distribution and clinical characteristics of patients with IgA nephropathy, suggesting that complement C3 may be a potential biomarker of IgA nephropathy and provide new ideas for its clinical management.