Abstract: To make full use of coking coal in Fushun mining area,a method of middlings re-cleaning is proposed based on cascade dissociation and substep recovery. In dense medium coal preparation technology,middlings,crushed to minus 3 mm,is successively delivered to hydrocyclone and spirals,while minus 0. 25 mm is polished; after rough grinding,clean coal from spirals is processed by rough flotation together with crushed coal minus 0. 25 mm,and then this flotation concentrate is separated again after fine grinding. The result shows that clean coal with yield of 39. 30%,ash content of 11. 49% is obtained when middlings with ash content of 31. 20% is crushed and then separated again.