Abstract: The evaluation methods, causes and prevention measures of nickel-based alloy welding hot cracking (solidification cracking, ductility dip cracking) are summarized. Combined with the characteristics of nuclear 690 alloy welding material, the effects of Laves phase, MC and M₂(C,N) carbide, MN nitride on solidification cracking and ductility dip cracking were investigated by large thickness crack test, and the hot cracking criterion of nickel-based alloy based on microstructure was proposed, the criterion for preventing solidification cracking was that the Laves phase content was not more than 0.9% (volume fraction), and the criterion for preventing ductility dip cracking was MC + MN + M₂(C,N) content not less than 0.18%. On this basis, a new 690 alloy welding material, WHS693M welding wire, was developed, which has excellent crack resistance and mechanical properties of deposition metal to meet the technical requirements of the manufacturing of third-generation nuclear power main equipment.