To reduce the crushing rate of brown rice, we studied the whitening process of brown rice, including numerical simulation and crushing analysis. Based on discrete element technology, we utilized EDEM discrete element system to establish a discrete element model of brown rice. The movement process of brown rice in the milling room was simulated under the conditions of different sieve edge number and roll structure, and the influence law of brown rice breakage was analyzed. The results showed that the brown rice in the regular quadrilateral sieve had poor motion along the radial direction of the sieve and weak tumbling ability in translocation, resulting in a low rate of rice breaking and the highest rolling pressure. Due to the weakest movement ability of brown rice in the regular octagon rice sieve, the brown rice grinding drops greatly, resulting the lowest broken rice rate. Additionally, with the increase of the number of grain, the radial velocity and rotational angular velocity of the brown rice in the milling room increased obviously, making a increasing broken rate. After reducing the diameter of the roller, the gap of shaft and screen in the milling chamber was increased. The whitening process of brown rice occurred uniformly, which resulted a lower crushing rate.