OBJECTIVE：To stu dy the improvem ent effect and mechanism of Guizhi fuling pill （GZFLP） on rats with phlegm-dampness type polycystic ovary syndrome （PCOS）.METHODS：Totally fifty female SD rats with regular estrous cycle were randomly divided into blank control group （n＝10） and model group （n＝40）. The model group received letrozole intragastrically [1 mg/（kg·d），for 21 d ] to induce phlegm-damp PCOS rat model. Forty model rats were randomly divided into model group ，metformin group [positive control ，0.135 g/（kg·d）] and GZFLP low-dose ，high-dose groups [4.49，17.96 g/（kg· d）]，with 10 rats in each group. Each medicine group was given intragastric administration ，once a day ，for 30 consecutive days. Blank control and model group were given intragastric administration of equal volume normal saline.After last medication ，oral glucose tolerance test （OGTT）was used to detect the level of blood glucose in rats at 0，30，60 and 120 min. ELISA assay was used to detect the levels of follicle-stimulating hormone （FSH），luteinizing hormone （LH），estradiol（E2）and testosterone （T）； body weight ，the weight of uterus ，bilateral ovaries and paragonadal fat were weighed. HE staining was used to observe morphological changes of ovarian tissue sections. RT-PCR method and Western blotting assay were used to detect mRNA and protein expression of CYP 19a1 in ovary and Glut 4 in uterine. RESULTS ：Compared with blank control group ，the levels of blood glucose 30，60，120 min after intragastric administration of glucose solution as well as serum levels of LH ，E2 and T were increased significantly in model group （P＜0.05）；the body weight ，the weight of uterus ，bilateral ovaries and paragonadal fat were increased significantly （P＜0.05）；the volume of thecal cells increased significantly and showed spherical shape ；the mRNA and protein expression of CYP 19a1 in ovarian tissue and Glut 4 in uterine tissue were decreased significantly （P＜0.05 or P＜0.01）. Compared with model group ，above indexes of administration groups were improved significantly （P＜0.05 or P＜0.01）；the thickness of theca cell layer and the volume of theca cells in GZFLP low-dose and high-dose groups were also improved. CONCLUSIONS：GZFLP can up-regulate the expression of CYP19a1 in ovary and Glut4 in uterus ，so as to improve the abnormal glucose metabolism in phlegm-dampness type PCOS model rats ，reduce insulin resistance ，lower serum estrogen levels ，and reduce the degree of polycystic changes in ovary ，thereby playing a role in the treatment of PCOS.