The invention relates to a method for producing low-carbon welding wire steel by a duplex process. The method comprises the steps of: desulfurization of molten iron by a mechanical stirring method, smelting of the desulfurized molten iron through a dephosphorization converter, feeding of steel discharged from the dephosphorization converter into a decarburization converter for smelting, refining of the steel discharged from the decarburization converter by a circular degassing method, ladle refining of the molten steel refined by the circular degassing method, and slab continuous casting of the molten steel after the ladle refining. The method for producing the low-carbon welding wire steel by the duplex process can guarantee excellent welding wire performances and improve the metallurgy quality of welding wires.