Prefabricated directly buried insulation composite plastic pipe is composed of polyethylene outer sheath pipe, polyurethane foam insulation layer and plastic working pipe (PPR or PE-RT).The insulation layer fills the gap between the inner and outer pipes closely, making the working pipes, outer protective pipes and insulation layer form a firm whole, which can effectively isolate the infiltration of air and water, and can play a good role of waterproof and heat preservation.The pipes made of these materials have the advantages of less heat loss, strong compressive resistance, good waterproof and anticorrosive performance, and long service life.