Abstract: In consideration of the property of the raw coal produced in Gaotou Mining Area in Dongshen coalfield, Inner Mongolia Autonomous Region, and the inadequacy of the existing coal cleaning process of the washery, the idea of the design of in-depth screening process is proposed. Through calculation of the calorific value of cleaned product, the optimum lower size limit of separation and most appropriate coal washing process are determined for the washery. Under the prerequisite of ensuring product quality, the washery is now capable of operating with much reduced volume of coal slime and all the production indices up to domestically advanced level, gaining, therefore, a favorable social and economic result.