The engine accessory gearbox is kinetic energy conversion device. In the test process, the vibration of accessory gearbox may monitor the working condition of gear. Aiming at the typical engine accessory gearbox vibration fault, using PULSE vibration analyzer, determined that the resonant frequency of the engine was the main cause. Application of hammering method test, verified that accelerometer mounted to the engine casing generated the system natural frequency resonance. Two methods reduce the accessory gearbox vibration level: Changing the natural frequency of the system through mounting an auxiliary weight on the bracket, avoids the generation of resonant frequency. Reducing the level of upper reducer vibration, reduces the influence on test system.