Drag force is a key parameter in the analysis of gas-solid flow,especially in dense vertical flows,and is important in numerical simulation of the gas-solid flow.To describe the cluster phenomena and their effects on drag force, a new model of gas-solid drag force is developed under the consideration of cluster effects using the energy minimization concept.Compared with the existing drag models,the new one can reasonably describe the interaction between gas and particle phase,and avoid the error caused by the inaccurate experimental coefficients.It can improve the accuracy of the simulation of dense gas-solid two-phase flow greatly.