Abstract: Pulverized coal is one of the important problems during the CBM well drainage. Aimed at pulverized coal with different diameters,the No． 11 coal of Taiyuan formation in Hancheng block was studied. Using different anionic dispersants,the experiment on screening dispersants was carried out. Dispersion stability of pulverized coal with differ- ent particle sizes was analyzed according to dispersing characters,suspension concentration and viscosity. The optimal dispersant in CBM well-washing technology was screened. The results showed that the dispersion stability changed in different degrees with the increase of the pulverized coal particle size,and the concentration of pulverized coal in each dispersant suspension was reduced with the growth of time. On the comprehensive analysis,the SDS dispersant per- formed the best for pulverized coal with size less than 200 μm,the CMN dispersant dispersed the best for pulverized coal in 200-300 μm. For the characteristics of pulverized coal in Hancheng block,the SDS dispersant had the best dispersion effect on pulverized coal and the SDS dispersant dispersion of pulverized coal was the most stable.