Abstract: 45CrNiMoVA steel and FGH96 nickel-based superalloy with significant microstructure differences but similar tensile strengths were used as the research objects. The 45CrNiMoVA steel was subjected to electrochemical hydrogen charging for 3–60 min, and FGH96 alloy was subjected to electrochemical hydrogen charging for 48–96 h. The 45CrNiMoVA steel charged with hydrogen for 60 min and FGH96 alloy charged with hydrogen for 96 h were subjected to hydrogen outgassing for 24–144 h and 24–120 h, respectively, by standing in the air. The influence of hydrogen on the tensile properties and fracture behavior of different materials was studied. The results show that after hydrogen charging, the percentage elongation after fracture and tensile strength of 45CrNiMoVA steel and FGH96 alloy significantly decreased compared to those in the uncharged state. With the extension of hydrogen charging time, the degree of tensile property degradation was intensified, and the hydrogen embrittlement index increased. However, the degree of property degradation of FGH96 alloy was significantly lower than that of 45CrNiMoVA steel, and its hydrogen embrittlement index was also lower. After hydrogen charging, the crack initiation location of 45CrNiMoVA steel shifted from the center of the sample cross-section before hydrogen charging to the outer surface, the initiation mechanism gradually changed from plastic-dominated to brittle-dominated, and the crack initiation zone and the propagation zone presented a mixed characteristic of indentations, quasi-cleavage and intergranular cracks; with the extension of hydrogen charging time, the quasi-cleavage area and intergranular crack density in these regions increased significantly. The hydrogen embrittlement mechanism of the 45CrNiMoVA steel was the synergistic effect of hydrogen enhancing local plasticity （HELP） and hydrogen reducing bonding performance （HEDE）. Cracks in both uncharged and hydrogen-charged FGH96 alloy were originated on the outer surface of the samples, and the fracture showed central ductile fracture and edge brittle fracture characteristics; with the extension of hydrogen charging time, the number of hydrogen-induced cracks on the surface increased, and the morphology of the brittle zone changed from quasi-cleavage to cleavage, with an increase in the depth of the brittle zone. The main hydrogen embrittlement mechanism of the FGH96 alloy was HELP mechanism, and the morphology of ductile fracture was not significantly affected by hydrogen. With the extension of hydrogen discharging time, the percentage elongation after fracture and tensile strength of the two materials were gradually returned to a state close to those under hydrogen-charging condition. The hydrogen-induced performance degradation mainly resulted from the reversible hydrogen diffusion behavior.