BACKGROUND The major reason for filtering bleb failure or scarring of the bleb site is due to excessive scarring after glaucoma filtration surgery in the clinic. Traditional Chinese medicine has preeminence in the prevention of fibrosis formation through the regulation of systemic circulation and improvement of the properties of the inflammatory cells in the blood. AIM To examine the clinical efficacy of using the Modified Cortex Mori Capsules (MCMC; Chinese name: Jiawei Sangbaipi Capsules) in the success rate of functional filtering blebs after glaucoma filtering surgery in clinical patients. METHODS Sixty resurgery glaucoma patients were randomly divided into two groups: 30 patients in surgery with the placebo group and 30 patients in surgery with the MCMC group. Patients took either the placebo or the MCMC 2 wk before and after surgery. Postoperative morphology and function filtering bleb, visual acuity, intraocular pressure, postoperative complications, the success rate of filtration surgery and clinical efficacy were observed. RESULTS Fifty patients completed the study. The percentage of functional filtering blebs in the surgery plus MCMC group was 84% at 6 mo after surgery, which was higher than surgery plus placebo group (64%, P < 0.05). The surgical success rate in the MCMC and placebo groups were 79% +/- 8.3% and 57% +/- 10.6% respectively (P < 0.05). The visual acuity, intraocular pressure and the postoperative complications in the two groups had no significant differences. CONCLUSION Glaucoma filtering surgery while taking MCMC not only reduced excessive scar formation and increased the success rate of functional filtering blebs but also improved the success of glaucoma filtration operations.