The effects of internals and gas distributors on the local dynamics of the bubbles in the conventional gas-solid fluidized bed were studied.Mesh-type internals with different opening areas(50％,70％and 90％)and different arrangements(two-layer and four-layer);and a sintered plate with a smaller pore size(1 μm)and a perforated plate with a larger pore size as distributors were investigated.Differential pressure drops and local solids holdups were measured under various superficial gas velocities to compare the performances of the different types of internals and distributors.The instantaneous solids holdup signals from the optical fibre probe were used to further examine the local bubble dynamics in detail.Smaller bubbles were found,with the installation of internals or using the sintered plate,resulting in lower pressure drops and a higher bed expansion.Internals with reduced opening area or distributor with smaller pore size further leads to a higher changeover rate between the bubbles and dense phase,both axially and radially,and hence a better gas-solid contacting and an earlier transition to the turbulent flow regime of the bed.