Nonstationary random signals have been the hot topic in domestic and overseas research recently. Mostly various signals studied in EMC are random jammer and nonstationary signals. The paper discusses stability judgement and feature extraction, proceeds to time-frequency analysis based on the Wigner-Ville distribution, and presents a practical example of radar jammer signals. The study can be applied to suppress jammer signals in EMC and offer jammer signal sources for experimental research by means of stimulation and emulation.