Small intestinal submucosa (SIS) treated via decellularization technology is a natural extracellularmatrix material. Because of its low immunogenicity and good biocompatibility, decellularized SIS is widely used for tissueregeneration and repair. However, the biological characteristics of SIS must be accurately understood to better transform andapply SIS in regenerative medicine. The function of SIS as a tissue-repair material depends on its composition andmechanical properties, the small molecules that the SIS degrades after being implanted, and the various properties andfunctions of these degraded molecules. This article reviews the physical and chemical composition, characteristics,processing method and applications of SIS to help understand the structure and function of SIS and promote its transformation and application.