Abstract: In this study, the CO methanation process in a three-dimensional bubbling fluidized bed with Ni-based catalyst is simulated with the reactive multiphase-particle-in-cell method, considering the complex gas-catalyst hydrodynamics, chemical reactions, and heat and mass transfer between phases. The consistency between numerical results and experimental data verifies the feasibility and accuracy of the model. The effects of operating parameters on the purity of CH4, the yield of CH4, the CO methanation performance, and gas-catalyst thermophysical properties inside the reactor are explored. The results show that the CO methanation process mainly occurs in the dense phase region. The fresh gas injected has a significant effect on gas and solid flux, and the heat transfer coefficient (HTC) of catalyst particles. A higher inlet gas velocity and operating temperature lead to a larger HTC of catalyst particles. Furthermore, the HTC of catalyst particles close to gas distributor is the largest, and then the dense region. The gas production of CH4 has an inverse relationship with the ratio of CO/H2. Increasing the CO/H2 ratio reduces the yield of CH4. Also, increasing the inlet velocity of gas decreases the reactant gases residence time, which results in the reduction of CH4 production.