The invention relates to a preparation method of macromolecular yak skin collagen capable of improving glycogen reserve of organisms. The preparation method comprises the following steps of (1) washing fresh or wetted and softened dry yak skin of peculiar wildyark growing in the region of Tibetan Plateau, putting the cleaned yak skin in an aqueous solution and adding an enzyme for enzymolysis, thus obtaining a hair-saved and hair-removed yak skin, (2) adding water to the hair-saved and hair-removed yak skin and then heating, and flushing with clear water to obtain an enzyme deactivated yak skin, (3) cutting the enzyme deactivated yak skin into small pieces and extracting with water to obtain a filtrate, (4) concentrating the filtrate and adding cold water to remove foam, thus obtaining a defoamed filtrate, (5) diluting the defoamed filtrate with water and separating to obtain a 14-25Kda macromolecular yak skin collagen solution, and (6) concentrating and drying the 14-25Kda macromolecular yak skin collagen solution to obtain the macromolecular yak skin collagen. The preparation method is simple and has remarkable effect, and the obtained yak skin collagen is concentrated in molecular weight distribution and has the function of improving the glycogen reserve of the organisms.