The invention discloses a preservative for clam. The preservative is prepared from the following components in parts by weight: 10-15 parts of chitosan, 10-15 parts of citric acid, 12-18 parts of glacial acetic acid, 12-18 parts of tea polyphenol, 5-8 parts of asparagus oligosaccharide, 1-3 parts of cecropin, 1-3 parts of sucrose ester, 1-2 parts of ginger powder and 30-50 parts of distilled water. Compared with the prior art, the preservative has the advantages that the natural color and flavor of clam can be effectively protected, moisture is maintained, and weight is increased; the structural elasticity and palatability of the protein body are well improved, and the original tenderness of clam is maintained at the same time, so that the product quality is effectively ensured.