Abstract: In order to assess the track irregularity of maglev lines, an analysis was made of the practical data of track-inspection acceleration signals of a high-speed maglev train, which indicates that the longitudinal vibration acceleration signal of the train guidance system is most sensitive to the long-wave irregularity of the maglev line. Hilbert-Huang transform is used to extract the intrinsic mode functions (IMFs) of the long-wave frequencies of the acceleration signals to obtain the instantaneous amplitude (envelope) and instantaneous frequency and then extract the long-wave irregularity signals. The proposed method was applied to analyze the practical data of a maglev train moving at a speed of 430 km/h, and the obtained long-wave irregularity signals of the maglev line agree with the ground survey results well.