NOVELTY - Benzoyl chloride and acrylic acid are mixed and distilled, to obtain acryloyl chloride. Amino acid is dissolved in buffer solution of sodium carbonate, and acryloyl chloride is dripped to obtained solution and stirred. Acetone is dripped to reaction mixture, and sodium carbonate is added to mixture and precipitated. Vinyl sulfonic acid functionalized monomer is added to mixture and precipitated. Free-radical initiator and hydrochloric acid solution are added to solution. The mixture is precipitated, washed and dried, to obtain acid-functionalized polymer catalyst.    USE - Preparation of acid-functionalized polymer catalyst used for synthesis of biodiesel.    ADVANTAGE - The method enables preparation of acid-functionalized polymer catalyst having excellent catalytic activity by economical and environmentally-friendly method with high yield.    DETAILED DESCRIPTION - Thionyl chloride and benzoic acid in molar ratio of 2-6:1 are added to reactor, heated for 0.2-1 hour, distilled under normal pressure and fractions are collected at 195-199 degrees C, to obtain benzoyl chloride. Benzoyl chloride and acrylic acid in molar ratio of 1-4/1 are mixed at room temperature for 0.1-0.2 hour, distilled under normal pressure, and fractions are collected at 70-75 degrees C, to obtain acryloyl chloride. The reaction system comprises 0.2-1% polymerization inhibitor with respect to monomer mass, to prevent the formation of free radicals. 0.01-0.04 mol Amino acid is dissolved in 20-60 mL buffer solution of sodium carbonate under ice-cooling, and 0.012-0.036 mol acryloyl chloride is dripped to obtained solution using a dropping funnel, vigorously stirred for 0.1-0.4 hour and maintained still for 4-24 hours. The reaction mixture is placed in beaker, acetone is dripped, constantly stirred, sodium carbonate is added to mixture, precipitated and supernatant is separated. pH of mixture is adjusted to 2 with 2-3 mol/L hydrochloric acid solution, and acetone is added to supernatant, and vinyl sulfonic acid functionalized monomer is added to mixture, and the mixture is precipitated, washed with acetone, stirred for 3-6 times and monomer is oven dried to constant weight. 1-3 g Vinyl sulfonic acid functionalized monomer is placed in a beaker, stirred at room temperature, and the mixture is dissolved in 20-60 mL deionized water, and pH of mixture is adjusted to 8 using 1 mol/L aqueous sodium hydroxide. Free-radical initiator and monomer (m1) in molar ratio 1:3 are added to solution and stirred at 40-60 degrees C for 0.5-2 hours. 3 mol Hydrochloric acid solution with concentration of 10-20 mL/L is added to reaction mixture, and 60-90 mL acetone is added to mixture at room temperature, precipitated, washed with excess acetone for 3-6 times and dried to constant weight, to obtain acid-functionalized polymer catalyst.