The floatability of lignite is usually known to be very poor. Generally, surfactants are applied to improve its hydrophobicity hi the flotation process. This research focuses on the adsorption performance of a nonionic surfactant, sorbitan monooleate, on the lignite particles with different densities, including 1.45 g/cm(3), -1.80+1.45 g/cm(3), and +1.80 g/cm(3). From Fourier transform infrared spectroscopy results, it was obvious that organic oxygen functional groups determined the surface properties of lower density lignite, whereas inorganic Si-O "determined the surface properties of higher density sample. Qualitative similarities are found in the curves of the surface electrokinetic potentials versus pH values. Points of zero charge of the samples were measured to be at pH values of 2.3, 3.0, and 3.0, respectively. Hence, organic oxygen functional groups are similar to Si-O on the coal surface in adsorbing OW and Er in electrolyte solution. The X-ray photoelectron spectroscopy results show that the lower density lignite particle has stronger adsorptions of sorbitan monooleate. In other words, organic oxygen functional groups have the priority over inorganic Si-O in adsorbing sorbitan monooleate. In addition, polar groups of the surfactant have different adsorbing abilities with organic oxygen functional groups. Interestingly, the oxygen content of +1.8 g/cm(3) lignite nearly does not change after the pretreatment by sorbitan monooleate solutions. Therefore, the sorbitan monooleate molecule almost cannot adsorb on the mineral surface.