Abstract: The characteristics of a supersonic oxygen jet at different environmental temperatures were studied by numerical simulation and compared with previous experimental results. It is found that the velocity attenuation of the oxygen jet is inhibited and the jet core length is extended under a high temperature environment compared with a low temperature environment. The jet temperature at different environmental temperatures becomes higher with oxygen diffusion and is close to environmental temperature finally. The jet pressure distribution has the same trend with the jet velocity distribution. The numerical simulation results of jet velocity, temperature and pressure have a relative high correlation with the measured values.