Abstract: The theoretical analyses of the hydrodynamics under a strong interaction flow regime were conducted and data of the bed averaged dynamic liquid holdup were obtained.The influence of gas and liquid velocity, liquid viscosity and packing materials on dynamic liquid holdup was investigated. The liquid superficial velocity has less significance on liquid holdup than gas superficial velocity.Actually it affects liquid holdup,especially under a mild pulsing flow regime.Liquid viscosity has no significance on liquid holdup,compared to gas and liquid phase velocity.The properties of the packed materials,such as lubricity,roughness etc.,were found to have a strong effect on liquid holdup.Based on the experimental data and theoretical analyses a new variety of correlation was proposed for dynamic liquid holdup under pulse flow,which was expressed as β_d=1.3242· γ · Re ^0.05666 _L· Re ^-0.3324 _g(for ceramic beads γ =1.0 and glass beads γ =1.42).The equation correlated the experimental data well and had good reliability in predicting dynamic liquid holdup under mild pulse flow.