The invention provides a crack defect resisting nickel-based welding wire for main equipment of a nuclear island and a preparation method and belongs to nickel base welding wires applicable to welding of the main equipment of the nuclear island. The welding wire is composed of, by weight, less than 0.04% of C, 0.10-0.20% of Si, 0.6-1.0% of Mn, less than 0.003% of S, less than 0.003% of P, less than 0.005% of S and P, 28.0-31.5% of Cr, less than 0.01% of Mo, less than 0.05% of Cu, 0.6-1.0% of Nb, 0.4-0.9% of Ti, less than 0.50% of Al, 8.5-10.5% of Fe, less than 0.005% of Ca, less than 0.005% of Mg, less than 0.005% of O, 0.20-0.40% of N, less than 0.001% of B, less than 0.005% of Zr, less than 0.02% of Ta, and the balance Ni and less than 0.10% of sum of other impurity elements. The problems that the as-welded 350-DEG C high temperature tensile strength of deposited metal of a current welding wire can not be greater than 505 MPa stably and crack defects occur easily on the severe conditions like field welding are solved.