This paper presents the simulative study of real time calibrated microwave radiometer based on the total power microwave radiometer. The simulation models of every section are built. In the simulative test

the mathematical means of discrete Fast Fourier Transform is used in signal processing. The contradiction of frequency resolving power and the number samples by the large span of frequency range is analyzed and relieved. The real time calibrated microwave radiometer is a new type of microwave radiometer. It can efficiently eliminate the influence of system gain fluctuations and effective system noise fluctuations. Thus

it is more suitable to spaceborne microwave remote sensing. The simulative results in this paper give an important reference to its optimizing design. Also they lay a foundation for the advancement of realizing spaceborne environment debugging.