Abstract: The large axialradial reactor for ethylbenzene dehydrogenation is a new type of radial flow reactor with catalysts self-sealing structure at the top of the bed,complex two-dimensional fluid flow in the catalyst bed.The continuity equation and the Ergen equation on the representative volume element are used to describe fluid flow in the axial-radial reactor in this paper,and the results are verified in a large cold model of size Φ 3000×10000.Flow fields are obtained by computer simulation with the finite difference method,and the effects of catalyst sealing length and flow direction on fluid field are discussed.The result shows that the fluid flow is mainly radial-flow at the radial section and mainly axial-radial flow at the catalyst sealing zone; Q _a/ Q is approximately equal to Q _r/ Q when δ equals 0.7 for centripetal flow and 1.1 for centrifugal flow, when δ is less than the values the fluid flow in the catalyst sealing zone is mainly axial-flow,when δ is bigger than the values the fluid flow is mainly radial-flow.Compared with centrifugal axial- radial reactor,centripetal axial- radial reactorcan limit the flux which flows through the catalyst sealing zone.