An acidic ionic liquid [N4H4(CH2)].4HSO4 was prepared with the raw materials of hexamethylenetetramine and concentrated sulfuric acid, and it was applied to the synthesis of ethyl chloroacetate. The technological parameters involved in esterification reation were optimized. Structures of the title compound and the catalyst were confirmed by 1HNMR. The results showed that n(chloroacetic acid):n(ethanol)=1:1.8, the amount of ionic liquid was 30% of the total mass of chloroacetic acid, the reaction temperature was 100℃, the reaction time was 3.5h and the yield of ethyl chloroacetate was 93.27%.When the acidic ionic liquid was repeated 6 times, the yield of ethyl chloroacetate was 90.16%. The product was easy to separate and the acidic ionic liquid overcomed the defects of inorganic acid catalyst.