This paper analyzes the interference mechanism of civil aviation VHF communications system and establishes a reasonable interference analysis model. The actual interference problems in VHF systems of civil aviation in Xi'an DMC are analyzed by using the proposed model. Firstly, the basic concept of radio frequency management is introduced, the concept of the electromagnetic spectrum and its characteristics are discussed, and the importance of the electromagnetic spectrum detection analysis and evaluation are discussed. Then the state-of-the-art technology of radio frequency management is introduced, the in-depth analysis of inter-modulation interference mechanism is conducted, the type and the generation mechanisms of the interference between civil aviation VHF system and FM broadcasting system are summarized. Finally, the intermodulation interference frequency analysis model is established from the two dimensions of frequency and power respectively, which can provide useful references for civil aviation planning and management of VHF communications system.