Abstract: Based on computational particle fluid dynamics (CPFD), an industrial grade polyethylene fluidized bed model in cold state was established to simulate the gas-solid flow characteristics in fluidized bed, and the image processing function of MATLAB was used to calculate the bubble size in the fluidized bed by matching the image pixels with the simulated grid. The effects of gas velocity and initial material quantity on the gas-solid flow characteristics of industrial grade polyethylene fluidized bed were studied from the perspectives of fluidized bed flow structure, particles and bubble. The results show that compared with the equipment in pilot and experimental stages, the side-wall effect in the industrial fluidized bed is obviously weak, and the dense-phase zone presents a more uniform particle distribution. The gas velocity has a great influence on the gas-solid flow in the fluidized bed. Under the operating condition of 0.46 m/s gas velocity, the particle distribution in the dense-phase zone is the most uniform, and the bulk flow becomes steady. The initial bed height mainly affects the height of the dense phase zone after fluidization, but has little effect on the bed expansion rate.