A welding wire for use in submerged arc welding of Cr-Mo steels comprising less than 0.25% C, less than 0.60% Si, 0.15-1.50% Mn, 0.50-10.0% Cr and 0.40-2.50% Mo on the basis of the weight ratio comprises 0.05-0.19% C, less than 0.60% Si, less than 1.6% Mn, 0.50-10.5% Cr and 0.30-2.50% Mo as the basic elements boron and nitrogen added thereto as the essential elements each in the range of 0.0001-0.25% B and 0.010-0.040% N; and at least one of titanium, zirconium and aluminum further incorporated therein each in the range of 0.01-0.30% Ti, 0.05-0.30% Zr and less than 0.40% Al, while being adjusting such that the sum of the elements: Ti+Al+Zr+10B lies within a range between 0.003-0.40% on the basis of the weight ratio. The welding wire of the novel composition can provide weld alloy steels with high strength and excellent toughness even at low temperature.