In order to simulate the radiative transfer characteristics of planetary atmosphere in the microwave and sub-millimeter wave bands, the absorption coefficient from 1 to 3000 GHz of the gases in planetary atmosphere are calculated by using line-by-line integration method. Based on the parameters of gas molecules in HITRAN database, such as the transition frequency, line strength and so on, the absorption feature of each gas molecule is simulated and compared with the common atmosphere radiative transfer model in microwave and sub-millimeter wave bands. As an example, the radiation transport characteristics of Earth's atmosphere are analyzed, and the atmospheric radiation brightness temperature of different frequency band using limb sounding method is simulated using the radiative transfer equation. The results can provide the model and theoretical basis for atmospheric composition detection simulation, the selection of detection frequency band and the retrieval of atmosphere profiles of Earth and other planets.
