Abstract: As one of the most abundant and widely distributed functional proteins in animal tissues and organs, collagen can be classified into types I, II, and III in the order of discovery, with type I collagen being the most common one. Collagen possesses good biocompatibility and degradability as well as low antigenicity, physical and mechanical properties, and has been widely used in recent years in many fields, such as food, biomaterials, animal husbandry, and medical aesthetics. In this paper, the chemical characteristics of modified collagen by different agents were introduced, including glutaraldehyde, chitosan, genipin, carbodiimide, and polyethylene glycol. Meanwhile, the application advances of collagen in the fields of medicine, cosmetics, food, and flexible electronic materials were summarized. Finally, the future promotion and application of collagen was prospected.