A fluidized bed was applied in a PM-removal device to remove PM2.5 effectively by the adhesion force. The effect of PM diameter on PM collection characteristics in the device was investigated experimentally. Numerical simulation was also performed to analyze the adhesion behavior of PM on the surface of particle in the fluidized bed and to compare the results with the experimental data. The experimental results show that the dominant factor of PM flow (except for flow resistance) changes from gravity to the adhesion force with decreasing PM diameter between 8.95 mu m and 2.25 mu m. When PM diameter is less than 2.25 mu m, PM is effectively collected by the adhesion force. Model predictions are in reasonably good agreement with the experimental observations. Model predictions indicate that PM is mainly collected in the area with a higher volume fraction of bed particles and is rarely collected in bubbles in the fluidized bed.