Objective:To explore the genetic polymorphism of cytochrome P450 enzyme 17(CYP17) and its relationship with the pathogenesis ofpolycystic ovary syndrome(PCOS).Methods:A total of 260 patients with PCOS of uyhan and han nationality in Xinjiang,who were admitted to Chinese Medicine Research Institute of Xinjiang Uygur Autonomous Region from January 2015 to February 2017,were chosen as PCOS group;the other 237 healthy fertile women,who were examined in the outpatient department during the same period,were chosen as control group.The CYP17 gene polymorphism in the two groups of subjects was detected by the restriction fragment length polymorphism polymerase chain reaction (PCR-RFLP) technique;the distribution of alleles and gene frequencies was compared between the two groups;combining with its clinical data,the relationship between CYP17 gene polymorphism and the pathogenesis of PCOS was analyzed.Results:Body Mass Index(BMI) and Follicle-stimulating hormone(FSH) levels in the PCOS group were lower than those in the control group;Luteotropic hormone(LH),Testosterone(TES) and LH/FSH levels in the PCOS group were higher than those in the control group,and the differences were statistically significant (P＜0.05).The frequencies of A1A1,A1A2,and A2A2 of CYP17 gene in the PCOS group were 34.62％,41.92％,23.46％,respectively,compared with 34.18％,43.88％,21.94％ in the control group,the difference was not statistically significant (P＞0.05).The allele frequency of A1 and A2 in the PCOS group were 55.58％,and 44.42％ respectively,compared with 56.12％ and 43.88％ in the control grouP,the difference was not statistically significant (P＞0.05).There was not statistical significance in FSH,LH and LH/FSH levels of different CYP17 genotypes in the PCOS group (P＞0.05).There was statistical significance in BMI level A2A2＞A1A2＞A1A1 and TES level A2A2＜A1A1＜A1A2 in the PCOS group (all P＜0.05).The BMI,FSH,LH,TES and LH/FSH levels of different CYP17 genotypes in the control group were not statistically significant (P＞0.05).Conclusion:CYP17 gene-34bp T/C nucleotide polymorphisms is a common base replacement in the population,which is not significantly related to the pathogenesis of PCOS.