Abstract: Screening is a key process link in coal preparation operations,and in-depth screening of fine coal has always been a difficult matter and a hot spot in coal screening operations. Based on the analysis of the drawbacks in cleaning of unclassified power coal and the status quo of the development of screening equipment industrial test on the feasibility of in-depth dry screening of power coal at a size of 3mm is made using the flip-flop screen and cross screen at the plant. As evidenced by the analysis and calculation,both screens can basically meet the demand in this respect in terms of screening efficiency. As compared with the previously used process of treating unclassified coal feed,the use of the new process can lead to improved quality and higher yield of clean coal product,as well as reduced production of coal slime. This is of great importance to the improvement of operating efficiency and economic benefit of power coal washery.