Background: Previous studies reported that the association between lipid levels and cognitive function related with gender, age and specific cognitive domains, but the influence of body mass index (BMI) on this association is limited. This triggered our interest in exploring how serum lipids relate to cognitive function in different subgroups. Methods: Data was collected from 2009 wave and 2015 wave of China Health and Nutrition Survey (CHNS). Multivariable linear regression analyses examined serum lipids level as predictors of sex- and age-specific measure of cognitive function in different BMI levels, which were adjusted for nationality, BMI, systolic blood pressure (SBP), diastolic blood pressure (DBP), smoking status, alcohol consumption and education level. Results: Cognitive function score have different concentration curves in serum lipids quartile levels in different BMI categories. After adjustment for confounding factors, serum TG was positively associated with cognitive function score in underweight (β±SE: 2.06±0.88, P=0.023) and obese (β±SE: 1.44±0.71, P=0.045) male group, and serum HDL-C was positively associated with cognitive function score in overweight (β±SE: 1.89±0.92, P=0.041) and obese (β±SE: 5.04±1.62, P=0.002) female group. Serum TC was negatively associated with cognitive function score in overweight (β±SE: -2.55±1.26, P=0.043) mid-life adults, and serum HDL-C was positively associated with cognitive function score in overweight (β±SE: 2.15±0.94, P=0.022) and obese (β±SE: 5.33±2.07, P=0.011) older adults. Conclusion: The associations of serum lipids with cognitive function were related with BMI levels and differed between gender and age groups. This result indicated that better nutritional status has superior cognitive function performance.