Abstract: In order to explore the modification mechanism of surfactants in wetting the low-rank coal of Shendong Coal Mine, a study is made of the wetting modification mechanism by making contact angle and Zeta-potential tests, FTIR analysis and molecular kinetic simulation with the use of three different surface active agents.Test result indicates that in terms of effects, the aniomic surfactant Triton X-100 is ranked first, followed by anionic surfactant sodium dodecyl benzene sulfonate(SDBS)with the cationic palmityl trimethyl ammonium chloride coming last.Zeta-potential test shows both anionic and cationic surfactants can all make significant change of surface electrical property of coal particles while the nonionic surfactant can produce only a minor influence in this respect.It is revealed by Zeta-potential analysis that the modification of surface wetting of coal particles is effected by adsorption of moleculars of surfactant on surface of coal particles.It is noted through molecular kinetic simulation that interaction of each of the 3 kinds of surfactants with coal particles assumes a negative value with the magnitude of the absolute value following the order of nonionic surfactant＞anionic surfactant＞cationic surfactant, indicating that the adsorption of nonionic surfactant on coal particle surface is far more stable.Furthermore, the use of the nonionic surfactant can enable the water moleculars to have a highest self-diffusion coefficient in coal-water system, signifying the nonionic surfactant exhibits a best wetting modification effect.This is in good agreement with the result obtained through the test.