The invention relates to a gas shielded welding all-position automatic outside welding system for pipes. The all-position automatic outside welding system consists of a welding car, an outside weldingcontrol system, a rail and a shielding gas system; a welding car is connected with the outside welding control system; welding actions of the welding car are controlled; the outdoor welding control system is on one side of a first pipe section to be welded; the shielding gas system is connected with the outside welding control system, and is on the other side of the outside welding control system; the rail is mounted on the first pipe section; and the welding car walks on the rail. The all-position automatic outside welding system is simple in gesture adjustment and high in efficiency in thewelding process, guarantees quick and accurate adjustment in the gesture welding process, improves the construction efficiency and the welding quality, saves car functions, adapts to the quality improvement difficulty, and improves the welding efficiency; and several part units of an outside welding machine are modular, so that installation and adjustment are easy, the maintenance difficulty is reduced, the maintenance time is shortened, and the construction efficiency is improved.