Gelatin is a polymer derived from the hydrolysis of collagen. As a natural polymer material with good biocompatibility and biodegradability, gelatin has been widely used in product packaging and thickening and as a delivery carrier due to its good foaming, emulsifying and film-forming properties. In this paper, the physicochemical properties of gelatin such as gel strength, viscosity, color, yield and isoelectric point and the factors influencing them are reviewed, as well as the modification of different types of gelatin, the types and ways of cross-linking of gelatin and the preparation of various functional gelatin-based hydrogels. Gelatin composite hydrogel adhesives with different functional properties can be synthesized by introducing different functional groups into different artificially designed materials, which can enrich the application of gelatin in daily life and provide some new ideas for the extraction and comprehensive utilization of gelatin.