The wavelet transform based on localized wavelet functions is applicable to analysis of pressure fluctuation signals from different flow regimes of a three-phase fluidized bed, which usually is nonlinear or nonstationary. The pressure fluctuation has been analyzed by resorting to the discrete wavelet transform such as wavelet coefficients, wavelet energy, and time-scale plane. The dominant scale of wavelet coefficients and the highest wavelet energy in the bubble-disintegrating regime are finer than ones in the bubble-coalescence regime. The cells corresponding to fine scale of time-scale plane in bubble-disintegrating regime are more shaded and energetic, while the cells corresponding to coarse scale in bubble-coalescence regime are more energetic. Therefore, the wavelet transform enables us to obtain the frequency content of objects in a three-phase fluidized bed locally in time.