NOVELTY - Preparing supported catalysts, comprises (i) preparing acidic ionic liquid by taking nitrogen-containing heterocyclic compounds, 1,4-butane sultone and ethanol solvent, and stirring under refluxing, filtering, washing with absolute ethanol, and drying, adding concentrated sulfuric acid, reacting, and adding ethyl acetate; (ii) preparing A1-MCM-41 zeolite carrier by dissolving cetyl trimethyl ammonium bromide in deionized water, and adding sodium silicate and aqueous solution of aluminum sulfate, aging, and calcining; and (iii) stirring acidic ionic liquid and carrier with anhydrous ethanol.    USE - The method is useful for preparing supported catalysts (claimed).    ADVANTAGE - The method produces catalyst with high activity, good stability, and which can be repeatedly utilized; utilizes less corrosive device; and has high recovery rate.    DETAILED DESCRIPTION - Preparing supported catalysts, comprises (i) preparing acidic ionic liquid by adding 0.10 mol nitrogen-containing heterocyclic compounds and 0.10 mol 1,4-butane sultone into 10-50 ml ethanol solvent placed in a round-bottomed flask, and then stirring at 50-80 degrees C for 3-24 hours under refluxing until a pale yellow solid is precipitated, and filtering under vacuum conditions, washing with 10-50 ml absolute ethanol added in an amount of 3 times, and drying under vacuum conditions, to obtain an intermediate product, and taking fresh round-bottomed flask, placing in an ice bath under stirring conditions, adding the intermediate product with 10-30 ml concentrated sulfuric acid in equimolar amounts, and then adding deionized water, reacting at 60-80 degrees C for 3-24 hours, to obtain crude acidic ionic liquid product, adding 10-50 ml ethyl acetate, washing thrice, and drying at 80-100 degrees C for 10-24 hours under vacuum conditions; (ii) preparing A1-MCM-41 zeolite carrier by dissolving cetyl trimethyl ammonium bromide (CTAB) in deionized water, stirring at 25-40 degrees C for 0.5-1 hour, until the solution becomes colorless and transparent, then adding sodium silicate and aqueous solution of aluminum sulfate, stirring by adding 0.5-2 mol/l sulfuric acid solution into reaction system by adjusting pH to 9-11, continuously stirring, and aging for 1-4 hours, where the molar ratio of silicon dioxide, aluminum oxide, CTAB and water is 1:5-160:0.1-0.5:100-140, loading the above solution into a stainless steel reactor, crystallizing at 100-140 degrees C for 3-6 days, filtering, adding deionized water in an amount of 3-5 times, drying at 60-100 degrees C for 8-16 hours, to obtain a white powder, and calcining at 550 degrees C for 6 hours in presence of air; and (iii) adding acidic ionic liquid and carrier in a mass ratio 0.1-0.5:1 into round-bottomed flask, adding 40-100 ml anhydrous ethanol, stirring under refluxing at 85 degrees C for 24 hours, placing the material into a rotary evaporation for taking out ethanol using a solvent, drying at 80-100 degrees C for 24 hours under vacuum conditions, to obtain the final product. An INDEPENDENT CLAIM is also included for use method of catalysts in the synthesis of biodiesel, comprising (a) taking fat or oil and short-chain alcohol in alcohol-oil molar ratio of 6-48:1 into a high pressure reaction kettle, adding catalysts prepared, adding 1-10 wt.% fat into catalyst, reacting at 100-160 degrees C for 1-10 hours, to obtain a mixture-containing biodiesel; and (b) filtering the step (a) mixture, filtering off by supported catalyst by continuously circulating, allowing the filtrate to stand and stratify, to obtain biodiesel and crude glycerol, and distilling under reduced pressure for separating short-chain alcohols, and recycling.