We investigated the flow behavior of polyethylene particles polymerized by Ziegler-Natta catalyst and Metallocene catalyst. The employed polymer particles were linear low-density polyethylene (LLDPE), and average particle size was 600 μm. Different flow behavior of polymer particles in a fluidized bed was observed with different polymerization catalysts in the bubbling and slugging flow regimes. The flow behavior determined from the pressure drop fluctuation in the lower and upper section of the bed was analyzed with statistical methods.