Abstract: Abstract To conduct blackening and phosphating surface treatment on 42CrMo alloy steel commonly used in high-voltage electrical products, methods such as metallographic examination, tensile testing, impact testing, hardness testing, fracture analysis, and mass fraction of hydrogen element testing were used to analyze the effect of different dehydrogenation interval time on material properties. The results show that after blackening and phosphating surface treatment, with the extension of the dehydrogenation interval time, the microstructure of the material was tempered martensite, the tensile strength and elongation at break of the material showed a decreasing trend, the impact absorption energy first increased and then decreased, the hardness change was small, the mass fraction of hydrogen element gradually increased. After blackening and phosphating surface treatment, the material was subjected to dehydrogenation treatment within 2 hours, and the dehydrogenation effect was the best.