Abstract: The hydrophobicity of lignite needs to be enhanced using surfactant because its surface is highly hydrophilic in nature. Study of lignite-surfactant interfacial action may lead to enhancement of flotation efficiency. A molecular structure model of the lignite produced in Xilinhot, Inner Mongolia is developed based on the structural parameters of the lignite obtained through test. The representativeness of the molecular structure is verified through comparison of tested and model-calculated infrared spectrums. Result of simulation indicates that: as the molecular of water forms a hydrated film on lignite surface under the electrostatic effect, the interfacial action between lignite surface with absorbed surfactant and water molecular is noticeably reduced; especially when the surfactant absorbed is sorbitan oleicacid ester, the water moleculars are seen to maintain an aggregative state high above lignite surface, which results in improvement of hydrophobicity of lignite surface due to the fact that absorption of water molecular is impeded; and the result of lignite flotation is in good agreement with the calculated result obtained through simulation.