The effects of gas velocity (0.10-0.68 m/s), distributor geometry (opening area ratio, number of orifices and hole sizes) and the particle size distribution (wide and narrow) of polyethylene on the pressure fluctuation of the distributor and the local pressure drop in the beds have been determined in a gas-solid fluidized bed of 0.07-m I.D. and 0.7 m in height. The mean amplitude and the normalized standard deviation of the local pressure drop were determined by analyzing pressure fluctuation in the bed. The variation of the mean amplitude of the local pressure drop with the gas velocity is independent on the different distributors. The normalized standard deviation of the local pressure drop increased with increasing the ratio of the excess gas velocity to the minimum fluidization velocity and the lumped parameter of the distributor, hD. Also, the normalized standard deviation of the local pressure drop of polyethylene polymerized by Metallocene catalyst (narrow) is higher than that of polyethylene polymerized by Ziegler-Natta catalyst (wide).