Abstract: In order to obtain an improved result in dry cleaning of the < 6 mm coal, the XDF multi-stage dry separator that works under the combined effect of vibrating force and air force is developed. Analysis on its structural design and working principle indicates that inclination angle of separating deck, vibration frequency, air quantity and feed rate are main operating parameters of the separator. Field application of the separator at Naryn Sukhai Coal Mine of Mongolia′s MAK company shows that for treating a feed with a size of 10～5 mm and an ash content of 19.53%, the gangue removal rate is up to 86.4% and the ash of the clean coal is as low as 7.74% while in the instance of treating a feed with a size of 5～1 mm and an ash of 17.13%, the above-mentioned two figures change to 80.2% and 6.67%, respectively, well demonstrating the efficiency of the separator in separation of small coal, in the abovegoing instances, the use of conventional compound dry separator cannot produce the up-to-standard clean coal product with an ash of less than 12.5%, while the use of the XDF separator, the yield of clean coal is 7 percentage points higher as well; the XDF separator can work with a lower separation density and a much higher separation sharpness and no middling product is produced in its separation process. Its other attractions include simpler product structure, elimination of middling recleaning process, wider separation size range, larger and faster waste removal capacity, and lower density of dust in circulating airflow, as compared with the conventional compound separator. The successful development of XDF multi-stage dry separator can effectively make up the deficiencies of the pneumatic separators currently available, and promote the use of dry method for cleaning < 6 mm small coal.