【Objective】Aiming at the significant degradation of air gap insulation performance of electrical equipment under high-altitude, low-pressure and low-oxygen environments, a study was carried out to character ize the flow propagation under different air pressures and oxygen contents. 【Method】By combining the fluid model with the plasma chemical reaction, a rod-plate electrode structure and a high-altitude low-pressure low oxygen air injection discharge simulation model were constructed to simulate the air injection propagation pro cess under different air pressures and oxygen contents, and to analyze the effects of air pressure and oxygen con tent on the injection propagation speed, electron density, injection channel radius and electric field intensity dis tribution. It analyzed the effects of air pressure and oxygen content on the propagation speed, electron density, channel radius and electric field distribution. 【Result】The results show that,with the reduction of air pressure, the flow injection propagation speed is accelerating, the flow injection head and channel electron density and electric field strength is decreasing trend, the flow injection channel radius on the whole increased; with the reduction of the oxygen content, the flow injection propagation speed is decreasing significantly, the electron densi ty is increasing, while the electric field strength on the whole increases, and the radius of the flow injection chan nel is decreasing. 【Conclusion】The factors of gas pressure and oxygen content have an important influence on the flow injection discharge characteristics and plasma reaction mechanism, which should be considered compre hensively in the actual engineering design.