The invention discloses a preparation method of tuna protein peptide. The method comprises the following steps of 1, firstly, selecting fresh tuna skin as raw materials, then, mixing the tuna skin andwater according to the ratio of 1:30, then, heating the mixture in a closed container to reach the boiling point, keeping the water temperature to 100 DEG C all the time, and in the process, obtaining a mixed solution after 2-3 h; 2, cooling the obtained mixed solution to 40-65 DEG C, then, adding an enzyme into the mixed solution, performing standing for 1-2 h, and then performing sufficient stirring; 3, the preparation method of the tuna protein peptide is high in yield, good in antibacterial activity and good in beautifying and skin moisturizing effect; meanwhile, the adopted raw materialscontain no hazard substances, no environment contamination is caused, the materials are wide in source, the preparation technology is simple, the product has the effects of maintaining beauty, keeping young, promoting cell growth and resisting aging, and the great important effect is brought into play for vital activity.