Regeneration of coked molecular sieve 5A was carried out in a nonadiabatic fixed bed reactor. Only port of the deposited coke in zeolite particles participated in the combustion reaction, while the remaining portion was removed in unoxidized forms. In addition, the reaction rate constant showed lower value than that obtained from a differential reactor. Johnson's model was satisfying for the prediction of the behavior of this regeneration process, and the maximum permissible oxygen feed concentration in an adiabatic system was calculated to be 1.0 mol%.