Abstract: Coking coal and fat coal are scarce coal resources which are main materials of quality coke for use in iron and steel making process.Nowadays, in most of the domestic coal preparation plants, the heavy medium separation process using high-efficiency H.M.cyclone as primary washing equipment is applied for separation of the coal.However, the process entails difficulties for effective recovery of the clean coal lost in middling product.As evidenced by analysis of the property of the coal treated by Qianjiaying Mine Coal Preparation Plant, it is feasible to recover the scarce sources through making fine and in-depth rewashing of the middling product after it undergoes appropriate liberation crushing process.The crushed middling is washed by 3-cone water-only cyclone in the first stage and retreated in spiral chute in the second stage.Flotation test made with the ground product of the second stage shows that the yield of concentrate is 47.42% with an ash of 11.5%, much increasing the recovery of clean coal.Development of the key technologies for in-depth and high- efficiency separation of coarse slime is vital significance for rational utilization of scarce coal resources and improvement of economic performance of enterprise.