Abstract: In simulation of microwave-induced rock damage, various achievements have been made in recent years, but most of them are based on the theory of continuous medium. This study has examined two-phase materials composed of quartz and plagioclase components under different discontinuity scales and different levels of exposure to microwave radiation, using the discrete element method of a particle flow code PFC2D. The results indicated that this method was successful in simulation of rock cracking process: initiation, development and coalescence of the cracks. And the micro-cracks were initiated at the boundary of high absorption phase, i.e. quartz crystals, expanding outward around and extending into the plagioclase material. Finally, a network of radial tensile cracks was mobilized. The simulated patterns of cracks agree well with those observed in experimental tests of microwave radiation. The results of the present study provide a new approach of numerical simulation to microwave-induced damage using the discrete element method.