The effect of superficial gas velocity and structural parameters of plate (perforated plate and tongue plate) on the hydrodynamics parameters of column are studied in a multi-stage bubble column, with 2000mm height and 282mm diameter of the multi-stage bubble column, by using the electrical resistance tomography (ERT) technique and computational fluid dynamics (CFD). According to the results, ERT and CFD techniques can be well applied to the measurement and estimation of gas-liquid two-phase processes. The gas holdups, the radial distribution of gas holdup and gas cap height strongly depend on the operating condition and tray structure. By increasing the superficial gas velocity, the gas holdup in the multi-stage bubble column increases. With a decrease of the open area ratio, the hole diameter and tongue angle, the gas holdups and gas cap height below the perforated plate increase. The addition of the perforated plate enhances the flow behaviour of gas-liquid in bubble column. The CFD can then aid the prediction of gas cap height and gas holdup in a multi-stage bubble column.