The invention discloses a preservative for aquatic products, basically comprising mussel lectin, chitosan oligosaccharide and camellia sinensis, wherein the weight of the components is that the mussel lectin is 10-20%, the chitosan oligosaccharide is 40-50% and the camellia sinensis is 30-40%. The aquatic products after being processed by the invention have no toxic harmless, ensure the safety of the food, and are good for environment-friendly. The mussel lectin of the invention can be mutually acted with glycoside ligands, such as glycoprotein, lipopolysaccharide and glycolipid, which are formed on surfaces of cell membranes of bacterium, and the growth of pathogenic bacteria can be inhibited. After the mussel lectin is combined with the chitosan oligosaccharide and the camellia sinensis, the invention has actions of controlling the bacteria and mould and resisting oxidation, the fresh-keeping period of the aquatic products is effectively prolonged, the aquatic products is not rotten, the color is not changed, the meat is not dry, hard and erosive, and the delicious taste is not reduced in the fresh-keeping period.