Fusion-bonded polyethylene (PE), ethylene-acrylic acid copolymer (EAA), epoxy (EP) powder, non-toxic polypropylene (PP), or non-toxic polyvinyl chloride (PVC) coatings are applied to the inner wall of steel pipes to create steel-plastic composite pipes with a coating thickness of 0.5 to 1.0mm. These pipes not only retain the high strength, ease of connection, and resistance to water flow impact of steel pipes but also overcome the drawbacks of steel pipes, such as corrosion, contamination, scaling, and the low strength and poor fire resistance of plastic pipes. Their design life can reach 50 years.