The invention discloses a fully-automatic flow production method of composite pipes. The fully-automatic flow production method comprises the following steps that sheet steel is rolled into steel pipes; PRT pipes are bonded with the exteriors of the steel pipes to obtain PRT composite pipes; PVC pipes are assembled at the exteriors of the PRT composite pipes to obtain the composite pipes; and foaming materials are injected between the PRT composite pipes and the PVC pipes. The problems that an existing composite pipe production technological process is discontinuous, multiple manual operationworking procedures exist, the production efficiency is low, and the automation degree is low are solved, and the composite pipes produced through the fully-automatic flow production method integrate multiple excellent properties of steel, PRT, PVC and the foaming materials, and have the advantages of being high in strength, good in plasticity and toughness, resistant to corrosion and heat, free ofleakage, resistant to impact, not prone to deforming and fracturing, good in thermal insulation performance, excellent in dielectric performance and the like.