A dynamic gear tester taking time-varying excitation of a bearing into consideration comprises a servo motor, a torque sensor B, a driving wheel support shaft, an active gear, a gear of an idle pulleysystem, a driven gear, a driven gear support shaft, a torque sensor A and a magnetic powder brake installed successively in a cooperative way. The three gears are provided with rotary encoders respectively, the two torque sensors are connected with a computer, the rotary encoders are connected with a data collection card and the computer, the servo motor and magnetic powder brake provide power and brake torque for the whole tester respectively, the torque sensors detects the torque of the whole tester, and the rotary encoders measure circumferential positions of the three gears in real time.Difficulty in testing dynamic characteristics of the gear transmission system influenced by time-varying rigidity excitation of the bearing in the prior art is overcome, dynamic characteristics of thegear transmission system with different types of bearing supports are tested and analyzed by experiment, and the measuring precision and stability are higher.