Abstract: The copper vapor generated by the arc ablation contact during the opening process of sealed DC contactors plays an important role in the arc characteristics and opening performance of the hydrogen-nitrogen gas mixture. In this paper, the physical parameters of the hydrogen-nitrogen gas mixture with different percentages of copper vapor are calculated based on the equilibrium plasma theory, and the influence of copper vapor is introduced to establish an arc model of hydrogen-nitrogen gas mixture based on the magnetohydrodynamic theory, and the influence laws of the copper vapor percentage and distribution law in the gas mixture on the arc ignition characteristics and arc development and evolution characteristics are systematically studied. Based on the disassembled cavity, simulated experiments were carried out to verify the arc re-strike probability and arc extinguishing time in the 750 V/250 A sealed DC contactor experiments, which are basically consistent with the theoretical analysis results. The study shows that, as the proportion of copper vapor in the gas mixture increases, the arc temperature decreases slowly, the arc extinguishing time increases gradually, and the probability of heavy breakdown increases; meanwhile, the uneven distribution of copper vapor decreases compared with the uniform distribution of arc extinguishing time. The results of the study provide theoretical reference for the optimization design of DC arc burning characteristics of mixed gas and highly reliable sealed DC contactors.