Accurate calibration is needed for Quantitative application of space-borne passive microwave radiometers. In this paper

the surface target which can be taken as the calibration reference target are studied

and the emission model was developed for the emissivity computation for these targets. It is found that in dense covered forest area

for 19-89GHz frequencies

microwave radiation brightness temperature can be calculated with an accuracy of 1K. For the frequency channel as low as 6 and 10 GHz

the desert area such as sahara can be taken as reference calibration target. And the established model accuracy in desert area is within 2K by using the NCEP reanalysis dataset as input.