Abstract: The content of unburned carbon in coal flying ash is an important index to judge its rank.The research subject of this study is the coal fly ash from a power plant in Shanxi province.Base on the analysis of the size characteristic of unburned carbon in the ash,the experiments on removing unburned carbon from ash were conducted.The results indicate that: the main size fraction appears in-0.045mm,under the condition of kerosene 12kg/t and octanol 2.0 kg/t,the ash containing carbon of 3.97% was obtained,the yield of the ash came up to 91.14%.The ash content of clean coal was 36.74%,whose net calorific power reached 5000cal/g.