Abstract: In order to improve the poor quality of coal water slurry from low rank coal and realize the efficient and clean utilization of low rank coal,nonylphenol polyoxyethylene ether( NPEO-40),a non-ionic surfactant,was used as dispersant to prepare low rank coal water slurry. The research on the slurrying performance and the mechanism of coal water slurry was carried out. The test of Shendong coal( SDC)low-rank coal water slurry shows that the apparent viscosity η100 of coal water slurry decreases with the increase of NPEO-40 dosage.When the dosage of NPEO-40 increases to 1.0%,the apparent viscosity η100 remains basically constant. When the dosage of additive is1% and the concentration of coal water slurry is 60%-68%,the slurry is a pseudoplastic fluid with shear thinning,and the maximum slurry concentration C1000 is 67.5%. When the concentration range of low rank coal water slurry is 60%-68%,the stability of slurry decreases with the increase of concentration. Isothermal adsorption studies show that the adsorption behavior of NPEO-40 on low rank coal surface is in accordance with Langmuir isothermal adsorption model and Gibbs free energy ΔGa0 dsis-29.27 k J/mol,proving that the reaction occurs spontaneously. The infiltrating experiment shows that when the dosage of NPEO-40 is 1.0%,it will be beneficial to the coal infiltration in the solution. XPS narrow-range scanning is performed on the coal before and after adsorption,and the content of C—C/C—H functional group decreases from 78.79% to 70.12%. The total amount of oxygen-containing functional groups C—O,C■O,and O■C—O increases from 21.21% to 29.88%,indicating that the hydrophobic functional group of NPEO-40 is combined with the C—C/C—H functional group on the coal surface after adsorption of NPEO-40. Therefore,the oxygen-containing functional group is exposed to the outside,thereby reducing the content of C—C/C—H functional group on the coal surface. The proportion of oxygen-containing functional groups increases and the hydrophilicity is enhanced,which is conducive to the formation of a hydration film. The pulverized coal particles are separated from each other through the hydration film,thereby reducing the flow resistance between the pulverized coal particles and achieving a viscosity reduction effect.