Objective：To explore the effects of epimedium total flavonoids on sex hormone in rats with polycystic ovary syndrome （PCOS）. Methods：Letrozole（1 mg/kg） was intragastrically administered in SD rats for 21 d to establish PCOS model. The PCOS rats were randomly divided into 5 groups（n=10）：PCOS model group，Diane-35 group（240 mg/kg），epimedium flavonoids group（50，100，200 mg/kg）. In addition，normal control group（n=10） was established. After continuous oral administration for 21 d，rat body weight and ovarian weight were measured and ovarian index was calculated. Serum testosterone（T），follicle stimulating hormone（FSH），estra－diol（E2），and luteinizing hormone（LH） were detected with radioimmunoassay. Results：Ovarian weight and ovarian indexes were sig－nificantly increased in PCOS group compared with those in normal control group（P<0.05）. Moreover，PCOS group had higher serum T，LH（P<0.001），LH/FSH（P<0.01） and lower E2 level（P<0.01）. After administration for 21 d，ovarian weight，ovarian index（P<0.05），serum T，LH（P<0.01） and LH/FSH（P<0.01） were decreased in 200 mg/kg epimedium flavonoids group compared with those in PCOS model group，but E2 level was significantly increased（P<0.01）. However，100 mg/kg and 50 mg/kg epimedium flavonoids had weak effects. Conclusions：Epimedium flavonoids can improve hyperandrogenism in PCOS rats，regulate LH/FSH，elevate E2 and improve ovarian function.