Abstract: There are three main factors to affect the cleaning result, they are rate of coal seams, lower size and separation density. firstly, the page determines the main factor by orthogonal analysis to simplify the three factors analysis into the two factors analysis. Secondly, the page simplify the complex data into intuitive graph by classification curve to determine the best separation conditions of the coal preparation plant. In the case of multi-factors, the integrated use of orthogonal analysis and classification curve is a new idea to determine the best separation conditions of coal preparation plant