Abstract: The 2-product H.M.cyclone originally used in Tianzhuang Plant's small coal cleaning system has been changed to a 3-product version for secondary cleaning of small coal middling product.Through readjustment of the size of the cyclone's vortex finder during the trial operation period, there have been seen an improved separation precision, increased calorific value of middling product, and improved clean coal quality and quantity indices.Furthermore, optimization of the medium purification-recovery system has led to lessening of difficulties in operation of small coal cleaning system and better control of medium consumption.