Collagen is a structural protein of extracellular matrix. It is a white polysaccharide containing a small amount of galactose and glucose. It is the main component of extracellular matrix (ECM), accounting for about 85% of collagen fiber solids. Collagen is a common macromolecular protein in animals, which mainly exists in connective tissues (bone, cartilage, skin, tendon, toughness, etc.). ), accounting for 25% ~ 30% of protein of mammals, equivalent to 6% of body weight. In many marine organisms, such as fish skin, the content of protein is as high as 80%. It plays a role in supporting, protecting, combining and forming boundaries between the body and organs. In addition to biomechanics, it also has the functions of signal transduction, growth factor and cytokine transport.