Abstract: The application of coal as raw material for the chemical industry is gradually shifted to the fine and high-end utilization. Ultra clean coal can be prepared by the deep removal of minerals from high carbon coal,which can be used as the raw material of high value-added advanced carbon materials. Using Taixi anthracite as raw material,the flotation experiment equipped by the self-made microbubble flotation column is optimized by Box-Behnken design method. The flotation concentrate under the optimum flotation conditions is analyzed by XRF,XRD and SEM-EDS. The process of deep demineralization by microbubble flotation method and the influence of different minerals on deep demineralization are further clarified. At the same time,NaOH-HCl method is used to deeply remove the minerals in anthracite. XRD and SEM-EDS are used to analyze the properties of de-mineralization samples,and the mechanism of demineralization and the reasons for limiting deep demineralization are further clarified. The microbubble flotation experiment shows that the optimum conditions are as follows:the dosage of collector is 3. 36 kg / t,the dosage of frother is 1. 81 kg / t,the agi- tation rate is 4 560 r / min,the ash content of concentrate is 0. 52% ,and the yield of concentrate is 66. 25% . The limit of deep demineralization in microbubble flotation are attributed to slime coatings and the existence of composite parti- cles with the particle size of less than 2 μm and the organic matter of more than 95% . The results of NaOH -HCl demineralization experiment show that the ash content of sample is decreased significantly with the decrease of sample size. When the average volume size of sample is 8. 01 μm,the demineralization effect is optimum. The demineralization of 86. 81% and ash content of 0. 36% can be obtained. The low reactive quartz and illite of Taixi anthracite and the fine silicate minerals coated by coal matrix mainly affect the deep chemical demineralization. Based on the limitation of deep demineralization of high carbon coal in both microbubble flotation methods and NaOH -HCl method,the deep demineralization method of flotation combined with chemical treatment is proposed for further deep demineralization of Taixi anthracite. Firstly,the total amount of minerals with low reactivity such as quartz and illite are reduced by flota- tion pretreatment. Then the minerals in flotation concentrate react with NaOH to form water-soluble sodium silicate and acid-soluble sodium aluminate silicate. Based on this mechanism, the descriptive model of deep demineralization process is further built up. The ultra-clean coal with ultra-low ash (0. 12% ),high carbon and high calorific value is finally obtained,which can be used to prepare high value-added carbon materials.