Pressure fluctuations experiments were carried out in a bubble column with a moderately large column of 0.376 m ID at different flow regimes such as bubbly and churn-turbulent flow regime. The recently developed technique of wavelet transform based on localized wavelet functions is applicable to analysis of the fluctuating signals. The time series of pressure fluctuation signals have been analyzed by means of coefficients of discrete wavelet transform, wavelet decomposition and timescale representation. By resorting to this technique, the objects in bubbly flow regime have fine scales than ones in churn-turbulent flow regime. Thus, this wavelet transform method enables us to obtain the scale content of local complex flow behaviors in a bubble column.