Abstract: For improving working efficiency of heavy medium cyclone in field operation, following an introduction of the working principle of the cyclone, an analysis is made of the factors influencing its working performance, with the focus on such factors as size of medium solids, content of fine slime in medium suspension, feed pressure, liquid-solids ratio, vortex finder orifice diameter and finder insertion depth, and diameter of underflow orifice. The laws governing the effect on coal separation efficiency exerted by each factor is brought to light. For facilitating the selection of each parameter, a reference is provided.