DVOR is an important direction-finding navigation system for civil aviation. Quickly and accurately monitoring the performance parameters of its space radiation field is the premise to ensure the safe operation of DVOR. Based on the extraction of DVOR space radiation field performance parameters and monitoring process using FFT, the solution process of using FFT to extract corresponding performance parameters is described in detail, a method of detecting the “notch” of DVOR FM-subcarrier by FFT is proposed, and gives the corresponding theoretical basis. The simulation experiments show that the corresponding performance parameters can be extracted quickly and accurately by using FFT; by changing the amplitude of the FM-subcarrier when there is no “notch”, the feasibility of the proposed “notch” detection method is verified, and obtain the basic criteria for the “notch” of judgment, the basic principle of “notch”, that is, when the amplitude of the FM-subcarrier at 10 080 Hz is 5.1 dBV lower than that of the FM-subcarrier without the “notch”, it can be judged that the FM-subcarrier has a “notch”.