Abstract: The domain division method for determining effectiveness factors of porous catalyst pellet is presented. By applying this method, the entire one - dimensional domain is divided into several equidistant subdomains and the nonlinear diffusion - reaction problems in a porous catalyst pellet are solved by using the one - point collocation method within each subdomain. In using the domain division method to determine the effectiveness factors of porous catalysts, a lot of calculations are made with power law type kinetic expressions and Langmuir - Hinshelwood kinetic expressions for three catalyst pellets. The agreement of the calculated results of this method with orthogonal collocation solution is satisfactory. The domain division method is simple for use and is not time consuming. The radius of dead zone can also be determined by using the domain division method, and the calculated results are reasonable.