Disclosed is a nickel base high temperature alloy welding wire used for a coal-fired power station and a preparation method of the nickel base high temperature alloy welding wire, and belongs to the technical field of welding materials. The preparation steps are that firstly, a mother alloy steel ingot prepared by a vacuum melting method is used to be forged into a square billet of 70 mm-110 mm, and then is forged into a square billet of 30 mm-50 mm; after heat preservation for 1 h-2 h by 1220 DEG C-1240 DEG C, and then a phi 5.0-phi 8.0 mm steel wire rod is hot-rolled; at last, the steel wirerod is made into a phi 1.0-phi 2.4 mm welding wire after continuous cold-drawing and intermediate heat treatment. The prepared welding wire welding joint deposited metal tensile strength is no less than 780 MPa, yielding strength is no less than 530 MPa, and room temperature shock is no less than 115 J. The nickel base high temperature alloy welding wire has the advantages that the nickel base high temperature alloy welding wire not only has higher deposited metal tensile strength, and meanwhile, has better tenacity and high temperature endurance strength.