Abstract: The attenuation mechanism of microwave was investigated according to the standard Maxwell equations of exhaust plume plasma.With a reference to the Shukla charging equation of particle components,the prediction method of microwave attenuation by weakly ionized exhaust plume plasma was presented.Radio frequency attenuation calculation(RFAC) software was designed and used to calculate the rules of complex conductivity and microwave attenuation constant that are influenced by some special exhaust plume field parameters.The RFAC and ThermoCalc propellant thermo evaluation system was used comprehensively to calculate the microwave attenuation by nozzle exhaust plume field that comes from two different kinds of propellant.The calculation consequences are in well agreement with the experimental results in citation.