Objective To investigate whether there are gender differences in the relationship between fasting blood glucose levels and non-alcoholic fatty liver disease （NAFLD）. Methods A retrospective analysis was conducted on 1，584 participants aged ≥ 40 who underwent health screening at Wuhan Union Hospital between January 2020 and November 2021. The cohort included 1，143 men and 441 women. Health screening indicators， including general demographic information and routine biochemical test data， were collected. Based on routine abdominal B-ultrasound scan results， participants were classified into NAFLD and non-NAFLD groups. The generalized additive model based on smooth curve fitting was used to describe the dose-response relationship between fasting blood glucose （FBG） and the risk of NAFLD in different genders. A two-stage logistic model was employed to reveal potential non-linear relationships， and threshold effect analysis was performed to determine the non-linear inflection point. Results FBG levels were significantly higher in the NAFLD group compared to the non-NAFLD group for both men and women. After adjusting for covariates such as age， BMI， smoking， alcohol consumption， hypertension， ALT， AST， TC， TG， HDL-C， and LDL-C， a positive linear correlation between FBG and NAFLD was observed in women， indicating that increased FBG was associated with a higher risk of NAFLD （OR = 1.29， 95% CI： 1.02 ~ 1.64）. In men， the relationship between FBG and NAFLD was non-linear. When FBG was ≤ 5.61 mmol/L， increased FBG was associated with a higher risk of NAFLD （OR = 1.58， 95% CI： 1.17 ~ 2.13）. However， when FBG exceeded 5.61 mmol/L， the risk of NAFLD plateaued. Conclusion There is a positive association between FBG and NAFLD in women. In men， NAFLD risk increases with FBG levels up to 5.61 mmol/L， beyond which the risk stabilizes， indicating a saturation effect.