To explore the expression of serum IgG in patients with IgAN and its clinical value on the prognosis of disease, a total of 429 patients with IgAN from February 2010 to October 2016 were selected in this study. Based on serum IgG level, these patients were divided into three groups. Group 1 with 144 patients with IgG < 8.12 g/L, Group 2 with 142 patients with IgG ≥ 8.12 g/L and ≤ 11.67 g/L, and Group 3 with 143 patients with IgG > 11.67 g/L. All the patients were followed up for more than 1 year. The clinical data collected before renal biopsy and the renal biopsy classification were compared, as well as the cumulative renal survival rates among the three groups. The results showed that there were significant differences in clinical data among three groups (P < 0.05). Patients in Group 3 had higher systolic blood pressure (SBP), lower hemoglobin (Hb), lower serum albumin, lower creatine, lower BUN, lower triglyceride, higher serum IgA, higher serum IgM, lower C3 and lower 24-hour urinary protein quantity than patients in the other two groups (P < 0.05). However, there was no difference in MEST-C classification among three groups (P < 0.05). The mean of follow-up days was 378 d. The cumulative renal survival rate in the first year among the 3 groups were 86.53%, 87.64% and 90.32%, respectively. According to Kaplan-Meier analysis, the cumulative renal survival rate of Group 3 was much higher than the other groups (P < 0.05). Thus, the study indicates that serum IgG level before renal biopsy is highly associated with prognosis of patients with IgAN, which might be a useful predictive biomarker.