Abstract: The philosophy and methodology of frequency spectrum analysis for complicated satellite systems are discussed. With a linear computation of any coupling working frequency bands of each satellite radio subsystem, the potential EMC problems caused by nonlinear interference, such as harmonic and inter-modulation, could be identified. The paper presents a frequency spectrum analysis software based on LabView and its application interfaces for practical satellite models. With the working frequency and information of radio frequency equipment as input of this software, any interference couplings between receivers and transmitters could be identified.