Twin arc welding system for offshore platform pile pipe with multipoint dual power and a singlemolten pool is put forward in this paper in order to solve the problems of low producing efficiency and operatinginconvenience in complex environment. Welding tractor，double welding gun adjusting mechanism and 120 degreescircumferential butt joint guide rail are designed. Monofilament AC manual gas protection welding machine internaltiming and motion motor are under real-time control Based on PLC. We elaborate the control requirement of thesystem，hardware configuration，software design and human-machine interface design，and complete the pile pipegirth welding test and technological parameter selection. The experimental results show that the system is stable andreliable，and the butt weld of the pile pipe is good，and the quality of the radiographic inspection is qualified，which fully meets the requirements of the construction of the pile pipe in the docking site of the offshore platform.