The use of PSP special injection molding pipe fittings has the advantages of light weight, low cost, long service life, reliable connection, convenient operation and maintenance, good sealing effect and concealed burial. It fundamentally solves the problems of high cost, inconvenient installation and connection, poor sealing effect and corrosion resistance of traditional steel plastic composite pipe fittings. Steel plastic composite pipe and double hot melt pipe fittings and connection technology include: steel plastic composite pressure pipe and double hot melt pipe fittings, special equipment related to connection, hot melt mold, process parameters and other technical contents. Steel plastic composite pressure pipe is formed by rolling galvanized (TIN) steel strip and argon arc butt welding steel pipe as the intermediate layer (Note: ordinary steel strip is used for medium and large diameter steel plastic pressure pipe above DN200); The inner and outer layer is polyethylene (propylene) plastic, which is compounded into a - body pipe by extrusion molding with special hot melt adhesive. The pipe system composed of steel plastic pipe and double hot-melt pipe fittings can be widely used in building water supply engineering, petroleum, chemical industry, pharmacy, food, mining, gas and other fields because of its reliable system, long service life, low comprehensive cost and convenient on-site construction and maintenance.