To determine serum levels of betatrophin in patients with polycystic ovary syndrome (PCOS) and the influential factors. A total of 100 PCOS patients were enrolled randomly as a PCOS group, and 40 age-matched healthy women were recruited as a normal control (NC) group. Primary clinical or biochemical parameters of the subjects were detected. The results were analyzed by SPSS 19.0. Serum betatrophin levels were elevated in the PCOS group compared with the NC group. Serum betatrophin levels were positively correlated with age and Whole Body Insulin Sensitivity Index (WBISI),and negatively correlated with body mass index, fasting insulin(FINS), homeostatic model assessment insulin resistance (HOMA-IR) and homeostatic model assessment β cell function (HOMA-β). Multiple linear stepwise regression analysis showed that age and waist hip ratio (WHR) were independent influential factors for the level of betatrophin. PCOS was more likely to occur in women with higher betatrophin levels. Serum betatrophin levels increase in women with PCOS and they are independently associated with age and WHR. There is no significant correlation between betatrophin and insulin resistance or insulin levels.