Co-extruded technology， as a kind of sausage processing technology with great technical challenge and good application， avoids the preparation and storage stage of the traditional sausage processing prefabricated casing， significantly improve the production efficiency and safety， and reduce the production cost， and have great market potential. Its preparation principle and processing point is to make the liquid on the surface of meat can be rapidly solidified into insoluble film in situ. In this paper， starting from the historical development of co-extruded sausage technology， the kinds of biopolymers suitable for surface film formation of co-extruded sausage and their physical and chemical properties are described， the importance of film forming raw materials and cross-linking technology is emphatically analyzed， and the advantages and disadvantages of different co-extruded sausage processing technology are summarized. It provides theoretical basis and technical support for future research， development， production and application of co-extruded sausage.