OBJECTIVE： To discuss the effect of Ethinylestradiol and cyproterone acetate tablet combined with metformin on ovulation induction of patients with polycystic ovarian syndrome （PCOS）. METHODS： 184 PCOS patients were randomly divided into control group （92 cases） and observation group （92 cases）. Control group orally received 1 Ethinylestradiol and cyproterone acetate tablet in 5 d of menstruation， once a day， it stopped after 21 d， the next cycle of treatment was started on the 5th of withdrawal bleeding. Observation group additionally received 3 Metformin tablet， once a day， without drug withdrawal during menstruation， and lasted for 3 menstrual cycles. After 3 menstrual cycles， all patients received ovulation induction treatment [（50-100 mg clomiphene was orally given from the 5th day of the 4th menstrual cycle， for 5 days， or 75-150 U postmenopausal gonadotropin by intramuscular injection， when the dominant follicle diameter was （19.0±2.0）mm， 10 000 U human chorionic gonadotropin （HCG） was intramuscularly injected， the ovulation was continuously monitored and whether there was ovarian hyperstimulation syndrome （OHSS） was observed]. Body mass index （BMI）， follicle estrogen （FSH）， luteinizing hormone （LH）， prolactin （PRL）， estradiol （E2） and testosterone （T） before and after treatment， fasting plasma glucose （FPG）， fasting insulin （FINS）， insulin resistance index （HOMA-IR）， pregnancy rate， ovulation rate and the incidences of OHSS and adverse reactions in 2 groups were observed.RESULTS： Before treatment， there were no significant differences in the BMI， FSH， LH， PRL， E2， T， FPG， FINS and HOMA-IR between 2 groups （P＞0.05）. After treatment， BMI， LH， PRL， E2， T， FPG， FINS and HOMA-IR in observation group and LH， E2 and FINS in control group were significantly lower than before， and BMI， PRL， E2， T， FPG， FINS and HOMA-IR in observation group were lower than control group， the differences were statistically significant （P＜0.05）. The pregnancy rate and ovulation rate in observation group was significantly higher than control group， the incidence of adverse reactions was significantly lower than control group， the differences were statistically significant （P<0.05）. And there was no significant difference in the incidence of adverse reactions between 2 groups （P＞0.05）. CONCLUSIONS： Ethinylestradiol and cyproterone acetate combined with metformin can effectively improve insulin resistance of POCS patients， recovery sex hormone secretion， promote ovulation and improve pregnancy rate， with good safety.