A dynamic model of the drive train of a megawatt wind turbine is proposed in which the blades, the hub, the main shaft, and the speed-up gearbox are assumed as flexibilities. The external excitation due to the measured load spectrum and the internal excitations due to the time-varying mesh stiffness, the transmission errors, and the meshing impacts within the gearbox are considered to predict the dynamic response of the system. Results show that the most vibration energy occurs at the speed-up gearbox, followed by the generator, and then the main shaft. An experimental remote real-time system is developed to monitor vibration performance of the drive train, with which the accelerations of components are detected. The experimental results are in accordance with the theoretical results.