The dense medium cyclone (DMC) is a high-tonnage device widely used to upgrade run-of-mine coal in the modern coal industry. It is known that a small improvement on the performance of DMC may greatly enhance industrial profitability. Therefore, it is very useful to develop an effective method to help optimize the design and operation of DMCs. Recently, based on the numerical experiments performed by Computational Fluid Dynamics and its combination with Discrete Element Method; the authors have established a PC-based mathematical model that looks promising to achieve this design and operational goal. In this paper, the authors will first discuss how to use this model to design high capacity or high efficiency DMCs for coal preparation through representative examples, in comparison with several typical designs in the industry. Some rules for DMC scale-up are then proposed for general application. The results further demonstrate that this DMC model can indeed offer a convenient way for optimum design and/or operation of DMCs under different conditions.