In this paper, a series of catalysts were prepared by impregnation loading of different amounts of phosphomolybdic acid and phosphotungstic acid on the montmorillonite modified by 25 % sulfuric acid as carrier. With XRD, nitrogen adsorption-desorption, and FT-IR characterizations, the structure of the catalysts was systematically analyzed, and the catalytic properties of the catalysts were studied in ethanol dehydration reaction to ethylene. The results show that. when WHSV was 2.5h-1 , the concentration of ethanol was 30%, the catalyst loaded with 10% of phosphotungstic acid showed excellent catalytic performance at 350 ℃, wherein the selectivity of ethylene was 99.9% and the conversion of ethanol was 98.9% The catalytic properties of supported phosphotungstic acid was more stable than supported phosphomolybdic acid, when the load amount increased to a certain value, the catalytic performance did not increase with the amount of loading further.