Abstract: In order to make a comparison of the separation performance of the 3-product H. M. cyclone and the 2-stage 2-product H. M. cyclone, the 2 versions of cyclones used at Gongwusu Coal Preparation Plant are taken as the object of study. Based on screening and float-and-sink data of the raw coal feed, clean coal, middling and reject samples collected from each kind of cyclone, a systematic comparison is made of the performance of the two cyclones in separation of each size fraction of the feed coal. Through the comparative analysis, it is made possible to make a quantifiable evaluation of cyclone performance and gain a scientific insight into the separation mechanism of H. M. cyclone.