ABSTRACT: This paper"s primary goal is to derive an approximate analytical solution to a mathematical model pertaining to a pore network model of deactivation of immobilized glucose isomerase in packed-bed reactors. To solve the previously developed mathematical model, the new approach to homotopy perturbation method is used. For all parameter values, the approximative analytical expressions for the steady-state concentration and current have been determined. The analytical solution and the numerical simulation exhibit excellent agreement. This work"s findings will aid in a better understanding of the examined mathematical model.