Experimental and numerical studies have been conducted on the effect of rotor blades in a mechanical impact mill. The flow fields and particle trajectories around the rotor were calculated using the CFD software, Fluent. Calcium carbonate and beta-cyclodextrin particles pulverized in the mill with various blade angles were characterized by particle size distribution analyses and X-ray diffraction (XRD). The optimum blade angle for changing crystalline property of the product is different from that required for size reduction. Fine particles are produced when the blades are inclined forwards at an angle of 30 degrees while the blades inclined at 15 degrees promote the efficient change in crystallinity of the product. From the CFD simulations, size reduction is related to the amount of normal impact energy of particles colliding with the blade and stator walls when the particles pass through the pulverizing zone. The change in the crystallinity of particles is related to the amount of tangential impact energy applied to the particles in the pulverizing zone.