The invention provides an ultralow-hydrogen high-toughness welding rod for welding of a water-diversion steel penstock in a hydropower station. A coating of the welding rod comprises, by mass, 40%-50% of marble, 2%-4% of dolomite, 18%-30% of fluorite, 2%-6% of quartz, 1%-3% of dehydrated feldspar, 1%-3% of zircon sand, 2%-4% of potassium titanate, 3%-6% of atomized ferrosilicon, 4%-8% of electrolytic manganese, 7%-12% of ferrotitanium, 1%-3% of light rare earth silicon iron, 0.5%-1.0% of ferromolybdenum, 2%-4% of nickel powder, and 0.5%-1.0% of rare earth fluoride. All the components are mixed according to the ratios to form the coating of the welding rod, potassium and sodium mixed water glass is added, an H04E welding core is coated with the mixture through a welding rod pressure coater, and the coated welding core is dried and shaped to form the electric welding rod. The deposited metal diffusible hydrogen content of the welding rod is 1.8 ml / 100 g, the low temperature impact toughness at minus 20 DEG C is stabilized within the range from 160 J to 180 J, and the welding requirement of the water-diversion steel penstock in a 610 MPa hydropower station can be met.