This study was designed to investigate the effects of Gleditsiae Spina (GS) on polycystic ovary (PCO) induced by estradiol valerate in female rats. We investigated the effects of GS on changes in body weights and food and water uptake for 5 weeks. In addition, we also examined the effects on ovary weights. Finally, we observed histopathological changes in PCO rats. Treatment with GS did not affect body weights, amount of food and water uptake compared with non-treated control group. Administration group of GS restored body/ovary weight ratio to normal levels, which were lowered by induction of PCO. In histopathological observation, formation of cysts was suppressed in GS group compared with non-treated control group. These results suggest that GS can be used for patients with PCO to prevent formation of cystic follicles and malfunction of ovary.