Objective:To compare the prevalence of non-alcoholic fatty liver disease (NAFLD) in women with or without polycystic ovary syndrome (PCOS), and to evaluate association between PCOS and NAFLD.Methods:A cross-sectional study was performed including 122 PCOS patients (PCOS group) and 107 age, and body mass index (BMI)-matched women (control group). Anthropometric parameters, liver enzyme, lipid profile, glucose and insulin levels, sex hormones and hepatic ultrasonography were measured in all subjects. The clinical features, laboratory parameters and prevalence of NAFLD were compared between PCOS group and control group. The related factors were evaluated between PCOS and NAFLD, finally the role of insulin resistance (IR) and hyperandrogenism (HA) was analysed.Results:Women with PCOS had a significantly higher prevalence of NAFLD than those without PCOS (62.6% vs. 76.2%, P=0.025). Logistic regression found that HOMA-IR and FAI were associated with NAFLD in PCOS women ( OR=1.686, 95% CI=1.279-2.223; OR=1.167, 95% CI=1.039-1.311), however, there was no significant correlation between FAI and NAFLD after adjustment for HOMA-IR ( P>0.05). Conclusion:NAFLD is more prevalent in women with PCOS than in those without. Insulin resistance and HA drive risk of NAFLD in young female with PCOS. IR may be an independent risk factor for NAFLD, and the association between HA and NAFLD is not independent but is mediated by IR.