Abstract: In this paper, CFD-DEM method coupled with the thermochemical submodel is employed to simulate the char combustion in a three-dimensional (3D) bubbling fluidized bed. The influences of particle properties on the particle profile, temperature, and reaction rates are investigated in horizontal and vertical directions. The results showed char particles with four types of diameters have the similar characteristic distributions and variation tendency to those with different densities. The major difference is that the particle-averaged char combustion rate increases with the particle size, but slightly decreases with the increment of density. The mixing index of fuel particles and the internal relation between particle mixing, heat transfer, and reaction are also explored. It is revealed that the particle content profile is apparently affected by the movement of bubbles. The uniformity of distributions of particle temperature, CO and CO2 concentrations is consistent with fuel particle profile in most cases.