Abstract: The preparation of pure low ash coal ultra-pure coal is the foundation of coal high value-added processing conversion and utilization. Low ash content and high yield of -1.4 g/cm3 haishiwan floating coal has the material conditions for the preparation of ultra-pure coal low ash pure coal. The composition and occurrence form of impurity minerals in low ash coal were studied by X-ray diffraction (XRD) and microscopic analysis of low ash coal with ash content less than 3%.It is found that the low-ash coal with ash content less than 3% can be obtained by gravity separation of haishiwan raw coal through the analysis of sieve floating-settling experiment. On this basis, grinding experiments are carry out under such conditions as selection of grinding method, grinding time, gradationmedium ratio and dispersing agent. The results show that wet grinding is better than dry grinding under the same conditions. When the particle size composition of grinding medium is smaller and the grinding time is longer, the grinding effect is better. With the addition of 0.55% sodium hexametaphosphate as dispersant, the mass ratio was 39.11%:23.57%:18.82%:18.50% when the diameter ratio of the grinding medium grinding gradation was φ30mm: φ25mm: φ20mm: φ15mm, wet milling for 4h and. At this time, the coal particles had been basically dissociated from the inorganic impurities. In this case, The the yield of cleaned coal was 19.08% and the ash content was only 0.88% by flotation of wet grinding of mineral.