Objective: To observe the effect of Yishen Capsule (益肾胶囊, YSC) on preventing the recurrence of chronic glomerulonephritis (CGN) and to explore its mechanism preliminarily. Methods:CGN patients were assigned to the treated group (61 cases) and the control group (48 cases) and all of them were orally administered with 4 mg of Perindopril twice a day, but 3 capsules of YSC, thrice a day,were given additionally to patients in the treated group. The therapeutic course for both groups was 18 months. The recurrence rate of CGN at the 6th, 12th, and 18th month in the two groups was observed and compared, and the changes of 24-h urinary protein quantity and T-lymphocyte subsets before and after treatment were observed as well. Results: (1) Comparison of recurrence rate between the two groups showed insignificant difference at the 6th month, but it did show significant difference at the 12th and the 18th month, which was significantly decreased in the treated group than in the control group (P＜0.05, P＜0.01); (2) The 24-h urinary protein quantity at the 18th month decreased significantly in both groups (P＜0.05, P＜0.01), but in the treated group was more significant (P＜0.01); (3) T-lymphocyte subsets showed no obvious change in the control group after treatment (P＞0.05), while in the treated group, it showed significant increase in CD3, CD4 and CD4/CD8 (P＜0.05 or P＜0.01) and significant decrease in CD8 (P＜0.05), and also the difference after treatment in T-lymphocyte subsets between the two groups was significant (P＜0.05 or P＜0.01). Conclusion: YSC has marked effects in reducing the recurrence of CGN and in decreasing urinary protein, and its mechanism might be related with its function in regulating the ratio of T-lymphocyte subsets to enhance the immunity of patients.