Abstract: Aiming at the direct calculation of two-dimensional model of effectiveness factor for a cylindrical catalyst pellet，this paper presents the construction of approximate analytical method and the corresponding accuracy test．A polynomial form is chosen to correlate the relationship between effectiveness factor and Thiele modulus(φ),where (1／tanhφ-1／φ）／φ is the element considering the features of two-dimensional problem.The needed values of parameters in calculation are provided by solving two-dimensional diffusion-reaction equations under extreme conditions.The accuracy is tested by first-order reversible reaction,steam-shift reaction and methanol decomposition reaction,and the results show that the approximate analytical method is not only simple but also has the same accuracy as the finite-element method or orthogonal collocation method.Further,it can be used in the problem of surface poisoned catalyst pellets．