Abstract: ERNiCrMo-3 nickel-based alloy welding wire was deposited on the surface of X70 pipeline steel by manual tungsten inert gas welding. The microstructure, element distribution and hardness distribution of the interface between the surfacing layer and base metal were analyzed. The initiation and propagation mode of hydrogen induced cracks were studied by electrochemical hydrogen charging method. The results show that the microstructure of fine grained region in heat affected zone of the interface between nickel-based alloy surfacing layer on X70 pipeline steel and base metal was fine ferrite and a small amount of pearlite. The microstructure of coarse grained region near fusion line was coarse ferrite. The microstructures of the fusion zone and surfacing layer were martensite and dendritic austenite, respectively. The impact fracture of surfacing layer showed a ductile fracture feature, the base metal showed a cleavage or quasi-cleavage brittle fracture feature, and fusion zone showed a mixture transition feature with deformation characteristics composed of shallow dimples and quasi-cleavage. The hardness of both the surfacing layer and fusion zone was higher than that of the base metal. The hydrogen induced cracks of the surfacing layer originated around the inclusions of Al₂O₃ and monatomic silicon, and propagation mode was intergranular and transgranular propagation.