Objective：To observe the expressions of interleukin-13（IL-13） in peripheral blood of patients with polycystic ovary syn－drome（PCOS） and to analyze their relationship with the body mass index（BMI），reproductive relevant hormone，fasting blood glucose （FBG） and blood fat. Methods：Clinical control trial was carried out. All patients were assigned to three groups：PCOS with obesity （40 cases），PCOS with non-obesity（35 cases） and controls（39 cases）. Body weight，body height，waist circumference and hip cir－cumference were measured and BMI and waist/hip ratio（WHR） were calculated. Enzyme-linked immuno sorbent assay（ELISA） kit for IL-13 was used to test the expression in peripheral blood. Chemiluminescence method was applied to detect FBG，fasting insulin（Ins），cholesterol（TC），triglycerides（TG），high-density lipoprotein（HDL） and low-density lipoprotein（LDL） level for the patients in three groups. Reproductive hormones including follicle-stimulating hormone（FSH），corpus luteum erythropoietin（LH），estradiol（E2），progesterone（P），prolactin（PRL） and testosterone（T） were assayed by radiation immunoassays（RI）. Results：Expression of IL－13 in peripheral blood was higher in PCOS with obesity than in PCOS with non-obesity（P=0.000） and that was higher in PCOS with obesi－ty and PCOS with non-obesity than in controls（P=0.000；P=0.019）. Serum levels of Ins，LDL，HDL，TG，TC，IR，E2，FSH and P were not statistically different. Serum levels of WHR，BMI，FBG，LH and T were higher in PCOS with obesity and PCOS non-obesity than in controls. Simple correlated regression analysis showed that IL-13 was correlated with BMI（R=0.527，P=0.000），FBG（R=0.449，P=0.000），WHR （R=0.272，P=0.021），LH（R=0.247，P=0.037） and T（R=0.452，P=0.000） and multiple linear regression formula was IL-13=90.814+1.255BMI+0.755WHR+1.696FBG+0.146LH+0.738T. Conclusions：Expression of inflammatory marker IL-13 is in－creased in the peripheral blood of PCOS patients and has positive correlation with BMI，WHR，FBG，LH and T indexes.