The invention provides a nickel-chromium-molybdenum alloy welding wire for surfacing welding of ball valves. The nickel-chromium-molybdenum alloy welding wire includes the following chemical components including, by mass percentage, 0.01% of C, not larger than 0.3% of Si, not larger than 0.5% of Mn, not larger than 0.015% of P, not larger than 0.01% of S, not larger than 0.2% of Al, not larger than 0.3% of Ti, 21.5%-22.2% of Cr, not larger than 0.3% of Fe, 8.5%-9% of Mo, 3.5%-3.8% of the sum of Nb and Ta and the balance Ni. According to the nickel-chromium-molybdenum alloy welding wire, the type and content of elements in the alloy composition are strictly controlled, an alloy is conveniently processed into thinner welding wires, and element ratio control helps to reduce the occurrence ofhot cracks during welding; and a vacuum smelting and electroslag double smelting process is adopted, and a refining method combining high-temperature instantaneous refining and low-temperature long-term refining is adopted in the vacuum smelting process, the purity and the degassing effect are further improved, the quality and performance of alloy ingots are improved, and plasticity and impact toughness are improved.