The steel-plastic PSP) composite pressure tube is formed by steel belt kun pressing and continuous argon arc butt welding to become a steel tube. It adopts the inner and outer composite plastic layers, and the middle is the composite structure of the reinforced welded steel tube. It not only overcomes the defects of steel pipe, such as easy corrosion, short service life, low strength and easy deformation of plastic pipe, but also has the common advantages of steel pipe and plastic pipe, such as good oxygen barrier, high rigidity and high strength , Buried pipes are easy to detect and so on. Because of its excellent performance, it can be widely used in construction water supply engineering, petroleum, chemical, pharmaceutical, food, mining, gas, optical cable and cable threading pipes and other fields, with good economic and social benefits and great promotion and application value. The early steel-plastic PSP composite pressure piping system, because of its production process: the steel strip is difficult to form, and the welding process is difficult. During the construction, the connection method of the pipeline is only the connection of the pipe fittings. Due to the large diameter of the PSP pipe, the copper pipe fittings and stainless steel pipe fittings used are costly; the cast iron pipe fittings have poor anti-corrosion performance and cannot ensure the service life of the piping system. But it is not widely used. Zhejiang Lianjing Co., Ltd. masters the most core precision forming welding technology of thin-walled metal welding, and steel-plastic composite technology. Through the research on the roughness of the steel-plastic composite pressure pipe in Zhejiang University, according to the structural characteristics of the multiple reinforced steel-plastic pressure pipe, the water flow conditions are simulated to provide guidance for the practical application of the pipe. Promote and implement new steel-plastic composite pipes and new electromagnetic double hot-melt pipe fittings connection technology at home and abroad.