Abstract: The feasibility study of re-cleaning middlings conducted on size composition of 50~0 mm size fraction and 0. 5~0 mm size fraction,as well as float and sink feature of 50~0. 5 mm size fraction in Tunlan coal preparation plant,three part,also conformed the re-cleaning process. The research result shows that the size fraction of middlings crushed to less than 3 mm,and separated by dense medium cyclone,the clean coal yield is 27. 78% with the ash content of 10. 50%,which obtained remarkable economic benefit.