Abstract: Direct current (DC) transfer switch is widely used in high voltage direct current (HVDC) transmission projects, and used for switching the operation mode of HVDC transmission system. The technical route of passive self-excited oscillation is mostly adopted, which has the advantages of simple structure and reliable performance. Therefore, the DC transfer switch is taken as the research object, then, through the analysis of SF₆ gas low air pressure characteristics, and in combination with the simulation analysis results of the air flow field of the arc-extinguishing chamber during the switching process of the DC transfer switch, the air flow channel is optimized, and a large-capacity switching device suitable for low air pressure environment is designed. The equivalent DC power supply of low-frequency oscillation current method is used to verify the current conversion ability of the DC conversion switch. The current conversion test is conducted at different currents and different gas pressures. The test results show that, with the reduction of the charging pressure of the breaking device, the current conversion ability decreases by 10% to 25%, and the arcing time is longer. Through simulation and experimental research, the result lays a foundation for the design of DC transfer switch and the evaluation of current conversion capability under low air pressure conditions.