The heat balance equation for the bulk temperature field of face-gear meshing was built, and the bulk temperature field distributions of cylindrical gear and face gear were studied under different geometric parameters and working conditions. Results indicated that face-gear bulk temperature was higher than that of cylindrical gear when the face-gear system reaching to bulk temperature. Moreover, the face gear bulk temperature showed a positive correlation with the rotate speed, load, environment temperature and gear surface roughness, and it showed a negative correlation with gear modulus, pressure angle and tooth numbers. The result provides initial temperature data of tooth surface nodes for the face-gear life prediction under the lack of lubrication conditions.