Based on loaded tooth contact analysis of spiral bevel gears, the thermal analysis model and finite element model of spiral bevel gears were established by making use of tribological theory and thermal transferring theory. The distribution on transient temperature field of spiral bevel gears under loss of lubrication was found via finite element methods. The results are as follows: the sliding speed and normal load had obvious influence on friction heat. Transient temperature peak value of the gear tooth was obtained in midpoint position of the tooth contact path. The temperature gradient increases with the increase of meshing times of gear tooth, the transient temperature of the gear tooth surface had increased 32°C in one minute. However, the transient temperature of the tooth surface had increased 232°C in three minutes.