Based on the climate environment of Heishan Open-pit mine, dry separation process was adopted to achieve coal quality improvement. In order to clarify the raw coal washability of thin coal seams of Heishan Open-pit Mine, the coal quality data were analyzed, the coal type and raw coal quality were determined, and the floating-and-sinking characteristics were analyzed. The separation test of 80-0 mm raw coal was carried out, the particle energy distribution in the bed was studied, and the bed density distribution in the separation process was determined. The response surface analysis was conducted to study the influence of various factors on the ash separation resolution, and the best sorting conditions were determined, and the sorting experiments were carried out, which verified the feasibility of the sorting technology. The results show that the washability of the thin coal seam in Heishan Open-pit Mine is medium.With the increase of frequency, amplitude and gas velocity (factors affecting energy change), the difference in density distribution and ash resolution show a trend of first increasing and then decreasing. Appropriate bed energy input is conducive to the separation and stratification of particles according to density. The response analysis show that ash separation resolution is highly sensitive to changes in various factors. When the frequency is 32 Hz, an amplitude is 2.8 mm, and a gas velocity is 0.6 m/s, the maximum ash resolution is 0.98. Under the optimal separation conditions, the separation density of 80-0 mm raw coal is 1.97 g/cm³, the E value is 0.22 g/cm³, the yield of clean coal is 74.92%, and the ash content of clean coal is 21.77%. After re-selection of 13-0 mm clean coal, The ash content is 6.79% lower than that of raw-clean coal, the comprehensive yield of 80-0 mm is 66.99%, and the ash content is 17.91%. The dry process can effectively improve the quality of the product coal of the thin coal seam of Heishan Mine.