The present invention relates to collagen and its preparation process. The preparation process includes eliminating foreign matter and scale from fish skin, washing, chopping in meat chopper, adding deionized water and heating inside a container, hydrolyzing with hydrolyzing proteinase, secondary hydrolyzing with flavoring hydrolase, heating to inactivate, letting stand to laminate, eliminating upper oil and grease layer, filtering the hydrolyze, defatting in a supercritical CO2 equipment, microfiltering to obtain filtrate, and spray drying to obtain collagen powder. The collagen powder has high solubility, high yield and good taste. The collagen may be used widely in food, cosmetics, medical supplementary material, enzyme and bioactive matter carrier, etc.