OBJECTIVE： To systematically evaluate therapeutic efficacy of modified Cangfu daotan decoction （MCDD） combined with chemical medicine versus chemical medicine alone in the treatment of polycystic ovarian syndrome （PCOS）， and to provide evidence-based reference for clinical decision. METHODS： Retrieved from PubMed， Embase， Cochrane Library， CJFD， Wanfang database， VIP and CBM， randomized controlled trials （RCTs） about MCDD combined with chemical medicine [ethynestradiol cycloprogesterone （Diane-35）， clomiphene， metformin] （trial group） versus chemical medicine alone （control group） in the treatment of PCOS were collected. After data extraction and quality evaluation with Cochrane 5.1.0 bias risk evaluation tool and Jadad scale， Meta-analysis was conducted for total response rate， serum hormone level （FSH， LH， LH/FSH， testosterone）， BMI， ovulation rate and physical signs （hirsutism， acne） by using Stata 14.0 software. Trial sequential analysis（TSA）was conducted by using TSA 0.9 software. RESULTS： A total of 20 RCTs were included， involving 1 484 patients. Results of Meta analysis showed that total response rate [RR＝1.13，95％CI （1.02，1.24），P＜0.05]， serum hormone level {FSH [WMD＝－0.59，95％CI（－0.98，－0.20），P＜0.05]，LH [WMD＝－0.95，95％CI（－1.41， －0.52），P＜0.05]，LH/FSH [WMD＝－1.04，95％CI（－1.78，－0.33），P＜0.05]，testosterone [WMD＝－0.93，95％CI（－1.38，－0.28），P＜0.05]}， BMI [SMD＝－1.01，95％CI  （－1.76，－0.27），P＜0.05]， ovulation rate [RR＝1.17，95％CI（1.02，1.34），P＜0.05] and physical signs {hirsutism [WMD＝－0.48，95％CI（－0.86， －0.10），P＜0.05]， acne [WMD＝－1.16，95％CI（－1.56，－0.75），P＜0.05]} of trial group were all better than those of control group， with statistical significance. TSA showed that there are reliable evidences for MCDD combined with chemical medicine in the treatment of PCOS. CONCLUSIONS： Versus chemical medicine alone in the treatment of PCOS， MCDD combined with chemical medicine can improve total response rate and ovulation rate， reduce serum hormone levels， BMI and physical signs.