Recently, the wavelet transform analysis based on the localized functions has been utilized to effectively analyze the pressure fluctuation signals. The pressure fluctuation signals can be decomposed into its approximations and details at different resolutions. By the wavelet transform, the time-frequency distribution of energy was described by the multi-resolution method. The result from the maximum energy of the approximations by wavelet transform analysis agreed with the result of the standard deviation analysis of pressure fluctuations. As seen from this study, the wavelet analysis in comparison with the standard deviation analysis, power spectral density function (PSDF), and the energy of PSDF enabled us to obtain the transition velocities, U-c and U-k, in characterizing the flow regimes of the fluidized bed.