Spontaneous coal combustion can produce a condition of heating process because the atmosphere of coal underground is usually poor in oxygen. Even though the spontaneous combustion of coal is prevented by people, the surface properties of coal are greatly changed. The changes in the wettability of coal influence the flotation of fine coals. This paper investigates the effect of the heating process on the wettability of fine coals of various ranks. Lignite, bituminous, and anthracite coals were used as experimental samples. The heating temperature and time were 500 degrees C and 2h. X-ray photoelectron spectroscopy (XPS) and contact angle measurements were used to indicate the changes in wettability of fine coals before and after the heating process. The results showed that the wettability of bituminous coal was significantly increased whereas that of lignite was greatly decreased after the heating process. However, the wettability of anthracite coal was increased only a little after the heating process.