A two-dimensional quasi-homogenous mathematical model has been developed on the basis of the two-dimensional flow model to simulate the axial-radial flow reactor for dehydrogenation of ethylbenzene to styrene under reduced pressure in this paper.The mathematical model is solved by using the finite difference method.The results show that the conversion of the axial-radial flow reactor is higher by 0.1%～0.6% than the radial flow reactor whereas the selectivity is approximately same and there is a low temperature and high styrene concentration area in the catalyst sealing zone.The model is verified by the data of a commercial axial-radial flow reactor for ethylbenzene dehydrogenation and can be used to guide its design.