Plastic-jacketed steel pre-insulated direct-buried pipe takes steel pipe as core, prefabricated integrally with polyurethane insulation layer and HDPE outer sheath. It features excellent heat preservation, waterproof and anti-corrosion performance with low heat loss. Direct burial saves construction space, delivers tight sealing and strong compression resistance. Anti-aging and long-lasting, it is widely applied in urban central heating, residential heating and industrial heat transmission pipelines.