Abstract: In order to improve the density of the low rank coal gasified coal water slurry and the efficiency of thegasifier,to reduce the coal consumption of the syng as and the oxygen consumption and to improve the service life of the nozzles in the gasifier,according to the property features of the low rank coal,the high concentratio n coal water slurry preparation technology with Graded Grinding Low Rank Coal and equipment were developed and the optimized stacking efficiency of the slurry was applied to improve the slurry density and quality.The practical applications showed that in comparison with the conventional slurry preparation technique with a single gr inder,the technique and technology could improve the slurry density with 3%5% and the grinding yield of the grinder could be improved over 30%.