The secondary refrigerant is an intermediate medium for transferring cold capacity, which can improved refrigeration efficiency. In this paper, the classification and characteristics of secondary refrigerants are introduced, and discusses the flow characteristics of secondary refrigerants and the apparent viscosity changes and flow resistance characteristics during the flow of secondary refrigerants. In addition, the application of different types of secondary refrigerants in aquatic product preservation and storage system is also discussed, among which non-phase change secondary refrigerant is mainly used in food impregnation and freezing. The phase change material refrigerant is mainly used in cold storage and refrigerating truck of aquatic product storage and transportation, and the future development direction of secondary refrigerant is prospected.