In this study, experiments are carried out for a high-pressure bubble column with a perforated plate as the distributor under the operating pressure up to 15 MPa. Gas holdups and pressure fluctuation signals are measured. Analyses of standard deviation and chaotic time series on pressure fluctuation signals are conducted to determine the transition gas velocities. The results of chaotic measures, such as the largest Lyapunov exponent, metric entropy and the correlation dimension show that there are bands of transition velocities for each operating pressure. The general trend is that the transition velocities increase as the operating pressure rises. Similar trends are also found for the transition velocities obtained by the standard deviation. All the transition velocities resulting from the chaotic measures and the standard deviation show good agreements.