Objective To investigate the association between body mass index(BMI),sex hormone and single nucleotide polymorphisms(SNPs)of follicle-stimulating hormone receptor(FSHR)gene rs2268361 and rs2349415 and its correlation with the risk of polycystic ovary syndrome(PCOS).Methods Peripheral blood was collected from 213 PCOS patients and 207 healthy controls,attending the Department of Reproductive Medicine at the First Hospital of Shanxi Medical University,and 32 follicular fluids were randomly collected from each of the PCOS and control groups from March to August 2021.Calculation of BMI of the PCOS and control groups;The levels of follicle-stimulating hormone(FSH),luteinizing hormone(LH),estradiol(E2),testosterone(T),progesterone(P)and prolactin(PRL)in peripheral blood of the two groups were detected by immunochemiluminescence method.Polymerase chain reaction(PCR)and high-resolution melting curve(HRM)were used to analyze the polymorphisms of rs2268361 and rs2349415 in FSHR of the two groups.Quantitative real-time PCR was used to detect the expression of FSHR gene mRNA in peripheral blood and ovarian granulosa cells.Results There was a strong positive correlation between LH and LH/FSH(r=0.88,P<0.05);The levels of BMI,E2,LH,LH/FSH and T in PCOS group were significantly higher than those in control group(P<0.05);FSH level was significantly lower than that of control group(P<0.001).HRM analysis showed the frequencies of CC,CT and TT genotypes at rs2349415 were 55.9%,34.3%and 9.8%in PCOS group and 68.6%,23.2%and 8.2%in control group,respectively.The frequencies of C and T alleles were 73.0%and 27.0%in PCOS group and 80.2%and 19.8%in control group,respectively.There were significant differences in genotype frequencies and allele frequencies between the two groups(P<0.05);The expression level of FSHR mRNA was higher in ovarian granulosa cells in PCOS group than in control group(P=0.004),the expression level of FSHR mRNA in rs2349415 TT genotype was higher than that in CC(P=0.002)and CT(P=0.035)genotype.Conclusion High levels of BMI, LH, E2 and T allele of rs2349415 increased the risk of PCOS.