Lignite is difficult to float because it owns high wettability. Furthermore, lignite can easily suffer the spontaneous combustion and magmatic intrusions which heat lignite from inside and have a heating impact on lignite properties. The heating process not only changes the physical and chemical properties of lignite but also changes its wettability. In this investigation, the changes in the wettability of lignite before and after the heating process were studied. The temperatures of the heating process were fixed at 500, 600, 700, 800, 900, and 1,000 degrees C. X-ray photoelectron spectroscopy (XPS) and contact angle measurements were used in the characterization of the wettability of lignite surface. Throughout this paper, it was found that the wettability of lignite could be decreased after the heating process. The lowest wettability of lignite surface could be obtained after heating at the temperature of 900 degrees C.