Collagen, a structural protein of the extracellular matrix (ECM), is the protein with the highest content and the most widespread distribution in animals. It is widely found in the skin, tendon, bone, cartilage, cornea and other tissues of animals. The dry weight of collagen in an adult body is about 3 kg. According to current reports, at least 29 kinds of collagen have been discovered. Collagen contains one or more tri-helix regions composed of α-chains, known as collagen domains; Natural collagen contains proline and hydroxyproline, which are almost not found in other proteins, and these two amino acids become the characteristic amino acids of collagen. Due to its unique structure and diverse biological effects, collagen has been widely used in wound dressings, tissue engineering materials, drug carriers, biological skin care, food and health products, cell scaffolds, biological 3D printing and other fields.