Objective To investigate the clinical effect of ethinylestradiol cycloproterone combined with metformin in the treatment of polycystic ovary syndrome (PCOS) with insulin resistance. Methods Ninety PCOS patients with insulin resistance admitted to the First People's Hospital of Taizhou from May 2017 to May 2019 were selected in the study.According to the random number table method, the patients were divided into control group and treatment group, with 45 cases in each group.The control group was treated with ethinylestradiol and cycloprogesterone, while the observation group was treated with ethinylestradiol and cycloprogesterone combined with metformin.The clinical effects of two groups were compared, including estradiol (E2), testosterone (T), luteinizing hormone (LH), follicle stimulating estrogen (FSH), insulin resistance index (HOMA-IR), fasting plasma glucose (FPG) before and after treatment.Body mass index (BMI) and fasting insulin (FINS) levels were measured.The ovulation, pregnancy, menstrual recovery and adverse reactions of the two groups were analyzed. Results The total effective rate of the treatment group (97.77%) was significantly higher than that of the control group (77.77%), the difference was statistically significant (χ2=8.389, P=0.003). Before treatment, there were no statistically significant differences in E2, T, LH, FSH between the treatment group and the control group (all P>0.05). After treatment, the levels of E2[(112.90±18.90)pmol/L], T[(1.30±0.78)nmol/L], LH[(8.00±1.50)U/L]and FSH[(1.20±0.39)U/L] in the treatment group were significantly lower than those in the control group[E2(128.90±19.95) pmol/L, T(2.19±1.00) nmol/L, LH(11.65±1.60)U/L and FSH(1.89±0.50)U/L], the differences were statistically significant(t=3.905, 4.707, 10.871, 7.299, all P 0.05). After treatment, the levels of HOMA-IR (2.19±0.50), FPG[(4.30±1.19)mmol/L], BMI[(22.40±1.89)kg/m2], FINS[(15.98±5.00)mU/L] in the treatment group were significantly lower than those in the control group[HOMA-IR(3.90±0.58), FPG (6.09±1.20) mmol/L, BMI (24.69±4.60)kg/m2, FINS (19.00±6.89)mU/L], the differences were statistically significant(t=14.979, 7.105, 3.089, 2.379, all P<0.05). The ovulation, pregnancy and menstrual recovery in the treatment group were significantly higher than those in the control group (χ2=4.121, 4.285, 10.000, all P<0.05). The incidence of adverse reactions in the treatment group (13.33%) was significantly lower than that in the control group (37.77%), the difference was statistically significant between the two groups (χ2=7.066, P=0.007). Conclusion Ethinylestradiol cycloproterone combined with metformin in the treatment of PCOS with insulin resistance has significant clinical efficacy, can alleviate the endocrine metabolic disorders and insulin resistance, it is worthy of clinical application and promotion. Key words: Polycystic ovary syndrome; Insulin resistance; Ethinyl estradiol; Gyproterone; Metformin; Sex hormones; Lipid metabolism