The invention discloses a single-arc twin-wire pipeline welding method, which belongs to the technical field of oil and gas pipeline welding. The method comprises the following steps of: machining bevels at pipe ends of two pipelines to be welded respectively and butting at the bevels of the two pipelines through butting devices in the pipelines; setting welding work parameters of a single-arc twin-wire pipeline full position automatic welding machine; preheating the pipe orifices to be welded to over 50 DEG C; and performing root welding, thermal welding, filling welding and cosmetic welding on the pipe orifices to be welded from inside to outside by using the single-arc twin-wire pipeline full position automatic welding machine respectively, until the circumferential surface of a weld joint is not lower than the surface of the outer wall of the pipeline, wherein the filling welding is performed on many layers; and the filling welding height of each layer is not less than 4 mm. According to the single-arc twin-wire pipeline welding method provided by the invention, the welding efficiency of a large-aperture thick wall pipeline can be effectively increased; and the single-arc twin-wire pipeline welding method has the advantages of large welding deposition rate, high welding speed, small heat input quantity, stable thermal affected zone, high weld joint mechanical property and the like.