The invention relates to a preparation method of a nickel-based alloy welding wire, and belongs to the technical field of welding material preparation. The preparation method comprises the following steps that 1, alloy smelting is carried out, specifically, the alloy comprises the following components of C, Si, Cr, Ti, Nb, W, Al, Fe, Mn, MO and the balance Ni; 2, ingot casting is carried out; 3, hot forging cogging is carried out, specifically, the alloy ingot is put into a heating furnace to be heated, forging is carried out, and an alloy blank is obtained; 4, hot rolling annealing is conducted, specifically, the alloy blank is hot-rolled into a disc round wire; 5, acid pickling, coping and cold drawing are conducted; 6, dehydrogenation annealing is conducted; and 7, auxiliary coating is carried out, specifically, the welding wire penetrates through a container containing auxiliaries, drying is carried out at the temperature of 18-30 DEG C, and the nickel-based alloy welding wire is obtained. According to the method, through the steps of metal raw material selection, alloy smelting, ingot casting, hot forging cogging, hot rolling annealing, acid pickling, coping, cold drawing, dehydrogenation annealing and auxiliary coating, the nickel alloy welding wire has good mechanical property, corrosion resistance and oxidation resistance.