NOVELTY - Synthesis of cefazolin acid, involves using dichloromethane as solvent, dissolving 7-amino acids in organic base to obtain 7-amino acid solution, using dichloromethane, reacting tetrazoleacetic acid and triethylamine salt with chlorinating agent for synthesis of anhydride or acyl chloride, dissolving obtained 7-aminocephalosporanic acid solution in acid anhydride or acid chloride, carrying out acylation reaction, carrying out extraction with water, adding prepared extract to methyl mercapto tetrazole and alkali, reacting, and carrying out acidifying crystallization.    USE - Synthesis of cefazolin acid (claimed).    ADVANTAGE - The method ensures industrialized production of cefazolin acid by simple and economical process, with less solvent usage, low environmental pollution, and high product yield.    DETAILED DESCRIPTION - Synthesis of cefazolin acid involves using dichloromethane as solvent, dissolving 7-aminocephalosporanic acid in organic base to obtain 7-aminocephalosporanic acid solution, using dichloromethane as solvent reacting tetrazole acetic acid and triethylamine salt with a chlorinating agent to form acid anhydride or acyl chloride, dissolving obtained 7-aminocephalosporanic acid solution in acid anhydride or acid chloride, carrying out acylation reaction at 60-100 degrees C for 30-120 minutes, carrying out extraction with water, adding prepared extract to methyl mercapto tetrazole and alkali, carrying out reaction at 50-90 degrees C, and carrying out acidifying crystallization. The chlorinating agent is pivaloyl chloride, phosphorus oxychloride, thionyl chloride or oxalyl chloride. The weight ratio of dichloromethane and 7-aminocephalosporanic acid is (2-100):1. The molar ratio of organic base and 7-aminocephalosporanic acid is (0.8-2):1. The molar ratio of tetrazole acetic acid and 7-aminocephalosporanic acid is (1-2): 1. The molar ratio of triethylamine and tetrazole acetiC acid is (1-2): 1. The weight ratio of water and 7-aminocephalosporanic acid is (2-100):1. The molar ratio of methyl mercapto tetrazole and 7-aminocephalosporanic acid is (0.8-2):1. The molar ratio of alkali and 7-aminocephalosporanic acid is (0.2-2):1.