To study the dynamic coupling feature of a self-synchronous vibrating system driven by two motors, two variable parameters to average angular velocity of two exciters and their phase difference were introduced, the parameters of the vibrating system were dimensionless processed, and then the synchronization condition and stability condition of the vibrating system were deduced. The dynamic coupling features of the two exciters of the vibrating system are quantitatively analyzed. The studies show that one half of product of the torque of frequency capture and the sine of phase difference between two exciters acts on the motor with the leading phase as load torque to decrease its angular velocity, and the other half acts on another motor with the lagging phase as driving torque to increase its angular velocity. The experiment to the vibrating system of the synchronization experimental table verify the correctness of the theoretical analyses.