In this work the effects of microwave heating on catalytic reaction systems are analyzed theoretically. In the modeling of the catalytic reaction system, the catalyst pellet was assumed to be composed of active site, support and fluid phase. Depending on the type of active sites, two cases were considered in this study: (1) a spherical active site on the flat support medium, and (2) a flat active site covered onto the flat support medium. For each case the temperature and concentration profiles within the catalyst pellet were obtained by simulation and compared with each other. When a chemical reaction was conducted with microwave heating, the reaction rate and the yield were found to be increased compared to conventional heating under the same conditions. This is due to hot spots generated by selective heating of the catalyst pellet, resulting in an increased reaction rate.