The invention relates to a preparation method of an ocean source metal-chelated peptide, and more particularly relates to a metal-chelated peptide prepared by enzymatically decomposing fishskin and scale protein by using a compound protease and flavourzyme. The metal-chelated peptide is prepared from ocean source fishskin or scale protein by steps of enzymolysis through compounding the compound protease and the flavourzyme, separation and purification, and freeze drying, and an amino acid sequence is gpagvkg. Researches indicate that polypeptide chelated calcium is easily absorbed, is safe and nontoxic, is low in price, and capable of simultaneously supplementing amino acids and calcium to become a preferred calcium-supplementing choice due to a special chelation mechanism and a transfer mechanism.