The invention relates to a processing method of fishes. The method comprises the following steps: (1) carrying out rough processing treatment on raw material fishes; and (2) carrying out fresh-keepingtreatment on the raw material fishes after the rough processing treatment. The fresh-keeping treatment specifically comprises the following steps: firstly, treating the raw material fishes by adopting a composite biological preservative, and then transferring the fishes to a cold storage for cold storage. The composite biological preservative is prepared from the following raw materials in partsby weight: 5-8 parts of lysozyme, 10-12 parts of nisin, 8-12 parts of fish bone peptide, 8-10 parts of glycerol, 15-20 parts of sodium chloride and 95-105 parts of water. The processing method of fishes provided by the invention has the advantages that good antibacterial performance can be guaranteed and the fishes are easy to clean. Meanwhile, the method has convenient process operation, and short processing time.