Dynamic infrared properties of high temperature hypersonic jetflow have been investigated.A numerical method was developed to solve the radiative heat transfer for non-gray absorbing,emitting and scattering medium by using the narrow-band model combined with molecular spectral access and the Mie scattering theory.The 2-5 microwave infrared properties of a high temperature jetflow including infrared images,spectral radiances,inband radiances and apparent source intensities were simulated at different altitudes.The results show that there are two distinct peak values in the jetflow spectra,and the spectral selection are similar at various altitudes.When the flight altitude begins increasing with ignition,the infrared spectral radiances increase until a certain altitude,and then get lower.At low altitude,the 2-3 microwave inband radiance are larger than the 4-5 microwave inband radiance,and the 4-5 inband radiance will become bigger than the 2-3 microwave inband radiance when the altitude increases.