Abstract: In order to understand the dispersant function and mechanism of the slurryability with a low rank coal, three dispersants of the sulfamate, sodium lignosulfonate and naphthal ene sulphonate were applied to the study on the slurryability performances of the lignite from Ordos Dongsheng Coalfield.The ultraviolet-visible spectrophotometer was applied to detect the ad sorption amount of the different dispersants on the coal surface, measured different dispersants affected to the zeta potential on the coal surface and discussed the dispersant type and amoun t affected to the rheological performances of the coal water slurry. The result showed that in the three dispersants, the sulfamate would have the best dispersion function of the coal water slurr y prepared with low rank coal and the compound of the sodium lignosulfonate and naphthalene sulphonate also would have an excellent dispersion performance. The dispersion performance a nd adsorption volume of the dispersant would have the coherence to the Zeta potential and the adsorption volume and the Zeta potential of the dispersant compounded would be obviously incr eased.The charged molecules of the dispersant would be adsorbed on the coal particles, thus the space hindrance of the coal particles would be increased and the electrostatic repulsion betw een the coal particles would also be enhanced. The joint role of electrostatic repulsion and space hindrance could obviously improve dispersion of coal water slurry.