[Background and aims]NAFLD is a common chronic liver disease. The purpose of this study is to carry out a current large-scale epidemiological survey and analyse factors related to the incidence and the severity of NAFLD.[Methods]Three communities of Shanghai were selected by stratified random sampling in 2019.The residents older than 18 years old underwent medical history taking, physical examination, laboratory examination and liver ultrasonography examination. The prevalence of different degrees of NAFLD, the prevalence of metabolic factors, and factors associated with the severity of NAFLD was analysed. [Results]A total of 19250 subjects were enrolled. The total prevalence of NAFLD in Shanghai was 45.55%, 62.00% in males and 27.54% in females. Age, FLI, BMI, WC, ALT, AST, AKP, GGT, CR, FPG, UA, TC, TG and LDL in NAFLD patients were higher than those in non-NAFLD people. The distribution of NAFLD prevalence was different in different age groups. The prevalence of diabetes, obesity and hypertriglyceridemia in the NAFLD group were higher than that in the non-NAFLD group. In males, FLI, weight, WC, ALT, UA, TG, GGT and metabolic syndrome were positively correlated with the severity of NAFLD; while HDL was negatively correlated with it. In females, age, FLI, weight, WC, ALT, FPG, UA, TG, LDL, GGT, AKP and metabolic syndrome were positively correlated with the severity of NAFLD; while HDL was negatively correlated with it.[Conclusions]The prevalence of NAFLD in Shanghai is high. The distribution of NAFLD prevalence was different in different age groups. Many factors are related to the incidence of NAFLD and the severity of NAFLD.