The crystallization purification process of crude cefaclor and its mother liquid by enzymatic method were studied.  With 7-amino-3-chloro-3-cephem-4-carboxylic acid ( 7-ACCA ) as the nucleus, D-phenylglycine methyl ester hydrochloride(PGM) as acyl donor, the catalyztic synthesis of cefaclor was carried out from immobilized penicillin G acylase (PGA) in the water phase. Then the obtained crude cefaclor and  its  mother liquid were crystallized and purified. Six factors during crystallization process were optimized, which are diluting agent and its dropping speed, pH, temperature, stirring speed and the amount of seed. Results show the cefaclor product obtained by dilution crystallization method has the advantages of stable crystal form, high purity low specific volume, good fluidable, and easy to packing.