Rotating units increasingly tends to automation, large-scale and high-speed development, and its composition and structure become more and more complex.However, the key parts of the gearbox is easy to damage under complex working conditions such as heavy load and high speed, and long-term operation. Discovering faults and predicting the development trend of faults in time under complex working conditions are the keys to fault diagnosis of rotating units. Aiming at the diagnosis problems faced by gearboxes of rotating units under complex working conditions, a fault diagnosis method was proposed combined with multi-sensor and D-S evidence theory. The example shows that the method can be used to effectively solve the fault problem of the gearbox, to ensure the safe, reliable and normal operation of the rotating unit, and to reduce the occurrence of safety accidents.