The invention relates to a preparation method of cefprozil. A synthesis method comprises the following steps: taking 7-ACA (7-aminocephalosporanic acid) as a starting raw material; after carrying outsilylation protection, carrying out a series of reactions including iodination and the like to generate a compound 2; taking the compound 2 to react with methyl D-(-)-4-hydroxy-phenylglycinate under the catalysis of immobilized penicillin acylase to generate a compound 1, so as to obtain a target product cefprozil. The preparation method provided by the invention has the advantages of moderate reaction conditions, environmental friendliness, high conversion ratio, simple technology and high cis-isomer content.
