Abstract: In Haiwan coal preparation plant of Shanxi province,plenty of slime has been produced in small coal preparation process,which caused series of problems including slime content in the whole system,yield of coarse or fine slime,final product quality etc.,in order to improve this situation,based on raw coal assay,the traditional separation technology is compared with precise sizing process. The analysis shows that: the precise process that raw coal is sized at 13（6） mm is superior to the traditional one,in which slime content is the only traditional process’ s that of 29. 73%（42. 38%） as well as yield of coarse or fine slime is the only traditional process’ s that of 23. 98%（35. 12%）,29. 74%（42. 37%） respectively; and calorific values of final product in these separation process are close,while yield of final product in precise sizing process is higher.