Abstract: 3NWZXΦ1300/920 type cyclone was used to sort raw coal with mud in Guobei coking coal preparation plant,and the effect of its production debugging is directly related to the normal production of coal preparation.The multivariate-one variable quantitative experiment was used to determine the optimum separation conditions,such as raw coal processing capacity,sorting density,feeding pressure,split ratio (slime content) and particle size.The quantity and quality of mixed clean coal maintains at a good level with the determined process parameters in actual production process.And at the same time,according to the problem of middling quantity of heat is excessive,the solution of using Sec overflow pipe inserted into great depth was proposed in this paper to increase middling ash under the premise of ensuring the clean coal ash.With the installation and commissioning of the overflow pipe,the calorific value of coal was controlled between 3500～3700kJ,and the yield was improved from 3.27% to 4.55%,which achieves the maximum economic efficiency.