The invention discloses a preparing method and application of an ocean polypeptide-calcium chelate.The preparing method includes the steps that protein in ocean animals and plants and leftovers thereof is extracted through an alkali-solution and acid-isolation method, or the ocean animals and plants and leftovers thereof are smashed and ground into thick liquid, protease is added into obtained protein or slurry to conduct enzymolysis, enzyme deactivation is carried out, and an ocean polypeptide compound solution is prepared; calcium in inorganic calcium chloride and ocean polypeptide are chelated to obtain the ocean polypeptide-calcium chelate, and the obtained ocean polypeptide-calcium chelate can be further prepared into leisure food, or dietary supplements or drugs.The preparation process is simple, the obtained ocean polypeptide-calcium chelate and products thereof have a unique chelation system and transport mechanism, are safe, nontoxic, easy to absorb and capable of supplementing amino acid and calcium at the same time, is the first choice of a calcium supplement and provides a new ideal for application of the ocean animals and plants and the leftovers thereof.