NOVELTY - Preparation of solid superacid catalyst comprises adding zirconium nitrate pentahydrate and cerium nitrate hexahydrate in water to fully dissolve; dropping ammonia water into the mixed solution under rapid stirring condition until the pH of the mixed solution is 8-9; producing the sediment; normal temperature aging the sediment; aging for 24-30 hours; filtering; washing by deionized water repeatedly; putting the sediment after washing in constant-temperature dry box; drying; grinding; steeping the powder with dilute sulfuric acid; drying; and roasting.    USE - Preparation of SO42-/ZrO2-CeO2 solid superacid catalyst used for preparing biodiesel (claimed).    ADVANTAGE - The catalyst has high catalytic efficiency in the production of biodiesel. The preparation of the catalyst is simple, non-corrosive to the reaction equipment, and capable of being separated from the product easily; has low cost and better reuse stability; and provides no pollution to the environment.    DETAILED DESCRIPTION - Preparation of solid superacid catalyst comprises:    (A) adding zirconium nitrate pentahydrate (Zr(NO3)4.5H2O) (A) and cerium nitrate hexahydrate (Ce(NO3)3.6H2O) (B) at 67:1-26:1 ratio, in water, which is in an amount to fully dissolve components (A) and (B); and magnetically stirring until the solution becomes transparent;    (B) dropping ammonia water into the mixed solution under rapid stirring condition until the pH of the mixed solution is 8-9; and producing the sediment;    (C) normal temperature aging the sediment by exposing in air for 24-30 hours; filtering; and repeatedly washing with deionized water until the pH of the filtering water solution is less than or equal to 7;    (D) putting the sediment after washing in constant-temperature dry box; drying for 12 hours at 100 degrees C; grinding; and steeping the powder with dilute sulfuric acid (H2SO4) for 0.8-1.2 hours; and    (E) drying the powder at 100 degrees C until the water completely evaporates; roasting in muffle furnace at 400-550 degrees C for 2-4 hours; and preparing solid superacid catalyst i.e. SO42-/ZrO2-CeO2.    An INDEPENDENT CLAIM is included for preparation of biodiesel using solid superacid catalyst comprising adding methanol and Jatropha curcas oil fatty acid at 2:1-4:1 volume ratio in high-temperature high-pressure agitated reactor; adding catalyst (6-10% of the fatty acid); putting the agitated reactor at 100-160 degrees C oil bath pot for 1-3 hours; reducing the temperature by water bath after completing the reaction; sucking the product through opening the agitated reactor; extracting with petroleum ether; heating for 4-6 hours in 90-110 degrees C constant temperature drying box to remove the petroleum ether; and obtaining biodiesel.