Background: Shenyankangfu Tablet (SYKFT) is a Chinese patent medicine that has been used widely to decrease proteinuria and the progression of chronic kidney disease. Objective: This trial compared the efficacy and safety of SYKFT, for the control of proteinuria in primary glomerulonephritis patients, against the standard drug, losartan potassium. Design, setting, participants and intervention: This was a multicenter, double-blind, randomized, controlled clinical trial. Primary glomerulonephritis patients, aged 18–70 years, with blood pressure ≤ 140/90 mmHg, estimated glomerular filtration rate (eGFR) ≥ 45 mL/min per 1.73 m2, and 24-hour proteinuria level of 0.5–3.0 g, were recruited in 41 hospitals across 19 provinces in China and were randomly divided into five groups: SYKFT, losartan potassium 50 mg or 100 mg, SYKFT plus losartan potassium 50 mg or 100 mg. Main outcome measures: The primary outcome was change in the 24-hour proteinuria level, after 48 weeks of treatment. Results: A total of 735 participants were enrolled. The percent decline of urine protein quantification in the SYKFT group after 48 weeks was 8.78% ± 2.56% (P = 0.006) more than that in the losartan 50 mg group, which was 0.51% ± 2.54% (P = 1.000) less than that in the losartan 100 mg group. Compared with the losartan potassium 50 mg group, the SYKFT plus losartan potassium 50 mg group had a 13.39% ± 2.49% (P < 0.001) greater reduction in urine protein level. Compared with the losartan potassium 100 mg group, the SYKFT plus losartan potassium 100 mg group had a 9.77% ± 2.52% (P = 0.001) greater reduction in urine protein. With a superiority threshold of 15%, neither was statistically significant. eGFR, serum creatinine and serum albumin from the baseline did not change statistically significant. The average change in TCM syndrome score between the patients who took SYKFT (−3.00 [−6.00, −2.00]) and who did not take SYKFT (−2.00 [−5.00, 0]) was statistically significant (P = 0.003). No obvious adverse reactions were observed in any group. Conclusion: SYKFT decreased the proteinuria and improved the TCM syndrome scores of primary glomerulonephritis patients, with no change in the rate of decrease in the eGFR. SYKFT plus losartan potassium therapy decreased proteinuria more than losartan potassium therapy alone. Trial registration number: NCT02063100 on ClinicalTrials.gov. © 2021 Shanghai Changhai Hospital