The effects of a catalytically reactive wall on ozone reduction are studied using a micro-DBD plasma reactor, where atmospheric non-thermal plasma is generated by a dielectric barrier discharge (DBD). We introduce a manganese dioxide catalyst on the internal wall of the micro-DBD plasma reactor. To evaluate the effect of the catalyst, three types of the reactors are prepared. The narrower gap length enhanced the catalytic ozone reduction for all of the reactor configurations. We constructed a model covering both plasma and catalytic reaction, and the numerical results conclude that the effects of catalytic reactive wall in the micro-DBD plasma reactor are explained by considering the acceleration of mass transfer from the bulk to the wall.