Abstract: The driven bevel gear of an aircraft center transmission device fractured after use of 95.85 h at the high altitudes. Macro analysis and metallographic examination were done to the fracture of the driven bevel gear, and microstructure, hardness and chemical composition were done to the fractured driven bevel gear. The results show that it was because the failure of rivet or aging of bonding agent that result in the sliding, friction and burning between the bush and the driven bevel gear great circle, and then cracks nucleated at the great circle of the driven bevel gear, expanded and finally fatigue fractured.