In the reclamation, a rotor with bits for a stabilizer is used to break the existing surface course layer in-situ on the road and mix and compact it with stabilizers such as cement or bituminous materials and the existing base course material to construct a new stabilized base course. The reconstructed base course quality (grain size and grain size distribution, etc.) is affected by the rotor bit arrangement and mixing speed. In this study, a three-dimensional discrete element method (DEM) was adopted to analyze the crushing and mixing behavior by the rotor of the stabilizer and the particle size distribution after mixing. The surface course layer consists of two layers with a surface course and a base course layer and was modeled by multi-diameter DE particles. In particular, a bond model was introduced between the particles of the surface course to reproduce the solidification forces between the particles that make up the surface course. The rotor model was geometrically modeled with 35 bits, a cutting-edge diameter of 1,150 mm, and a width of 700 mm. The analysis reproduced the contact behavior between the rotor and the surface course layer by moving the rotor model at the mixing depth of 350 mm and the rotor travel speed of 1,500 mm/min and investigated the motion (crushing, mixing, and reconstructing) of the particles that make up each layer.