Abstract: A numerical simulation of the gas-solid flow in a chemical looping gasification fuel reactor (the lower and upper part is designed as gasification and reforming reactor respectively) was carried out in this paper based on the multiphase particle-in-cell (MP-PIC) method. The sensitivity of the drag force model and the model parameters (normal-to-wall and tangent-to-wall momentum retention e_wn and e_wτ) to the simulation results were verified, and appropriate models along with model parameters are determined. The effect of gas velocity and slit size at the interface between the two beds on the particle flux was investigated. The results show that the particle flux increases with gas velocity but decreases with slit size.