Abstract: The solid superacid SO42-/ZrO2 supported on mesoporous MCM-48 was prepared by the liquid-phase precipitation，and the process for the formation of superacid on the catalyst surface and mechanism of regioselective nitration by catalysis were presented. The regioselective nitration of o-xylene with nitric acid was selected as a probe reaction to test the catalytic performance. The structure of the solid superacid was characterized with acid base titration，TEM，N2 adsorption/desorption and Hammett indicator. The results showed that the mesoporous structure of MCM-48 was maintained in the catalyst system，and there were Brønsted acid and Lewis acid sites on catalyst surface with a high BET surface area of 208 m2/g and better solid acidity (H0＜－13.75). The optimum conditions were as follows：calcination temperature of catalyst was 500 ℃，the reaction was carried out at 60 ℃ for 3 h with n(nitric acid)/n(o-xylene) 2.5 and m(o-xylene)/m(catalyst) 25 to get the yield of 91.8%，the content of product up to 82.1%.