Objective To analyze the relationship between trans fatty acid （TFA） intake and mild cognitive impairment （MCI） in Chinese residents.Methods Based on the 2018 survey data of the China Health and Nutrition Survey， subjects aged ≥40 years and those with completed data of demographics， lifestyle， disease history， dietary survey， cognitive assessment and physical measurement were selected. Data on food consumption collected by three consecutive 24 h dietary recalls， combined with food TFA composition data were used to assess daily TFA intake amount. The Chinese version of Mini-Mental State Examination （MMSE） was employed to measure global cognitive function and MCI was further identified. The association between TFA intake amount or groups by quintiles （<0.55， 0.55~0.90， 0.91~1.31， 1.32~2.13 and ≥2.14 g/d） and MCI was analyzed by multivariate Logistic regression and their dose-response relationship was explored by restricted cubic spline.Results A total of 4 507 subjects were included. The median （P₂₅， P₇₅） intake of TFA was 1.09 （0.64， 1.84） g/d， with MCI prevalence was 19.1% overall. The prevalence of MCI across quintiles of TFA intake was 20.7%， 19.2%， 17.0%， 16.8% and 21.9%， respectively. The differences were significant （P=0.030 7）. After adjusting for confounders （age， gender， education attainment， household income， marital status， residence， smoking， alcohol intake， physical activity， energy intake， choronic disease history and BMI）， TFA intake significantly increased the likelihood of MCI （OR=1.057， 95%CI： 1.004-1.111）. The probability of MCI in the Q5 group was 1.338 times higher than that in the Q1 group （95%CI： 1.031-1.739）. There was an interaction between age and TFA intake on the likelihood of MCI （P=0.014 5）， the likelihood of MCI in the Q5 group in subjects aged 40-64 years relative to Q1 （OR=1.537， 95%CI： 1.074-2.212） was higher than that in ≥65-year-old group （OR=1.135， 95%CI： 0.763-1.688）.Conclusion Higher TFA intake may increase the prevalence of MCI in Chinese residents aged 40 years and older. Reasonable diet and reducing TFA intake are of great significance to decrease MCI.