Electrical resistance tomography was applied to non invasively visualize the liquid distribution in a lab scale trickle bed reactor. Based on the three-dimensional liquid distribution images (Lime and two dimensional space) obtained by the ERT system, effect of the physical properties of the fluids and the packed bed, such as column size, particle diameter, gas density and liquid viscosity, on the pulsing flow regime transition and the liquid pulse structures were clarified. The liquid pulses structures were basically dominated by the small local pulses generated in the capillaries between the packed particles. Promotion of the local pulses generation makes the macro liquid pulses evident and well separated, while restriction of the local pulses generation results in the not fully developed or transient liquid pulses. Moreover, basic hydrodynamic parameters characterizing the pulsing flow, namely the liquid pulse velocity and frequency, were also quantitatively discussed. Liquid pulse velocities were calculated by the cross correlation of the conductivity variations of two ERT sensor with certain distance. The effective liquid pulse frequency which only includes the contribution of the main liquid pulse was determined by identified number of main liquid pulse from the 3D liquid distribution images provided by ERT. The measured liquid pulse velocity and frequency by ERT were then compared with the correlation models proposed in previous literatures. (C) 2015 Elsevier Ltd. All rights reserved.