A discrete particle motion-collision decoupled model based on dense gas molecular dynamics and gas-solid two-phase fluid dynamics of dense gas-solid flow in the fluidized bed was developed. Particle collision was modeled by means of the direct simulation Monte Carlo (DSMC) method.The large eddy simulation(LES) accounting for the effect of particle fluctuation was used to model gas turbulent flow. The Newtonian equations of motion were solved for each individual particle in the system. The interaction between gas phase and particle phase was determined by means of Newtonian third law. The flow behavior of gas and particle phases were numerically simulated in a circulating fluidized bed. The distributions of gas and particle velocity and particle concentration in the riser were analyzed.The number-averaged duration time

the ratio of total cluster duration time to total observation time and the cluster frequency were obtained in the circulating fluidized bed. The simulated results were in agreement with experimental measurements of literatures in the circulating fluidized beds.