Aiming at the vibration response of planetary gearbox, the vibration signal model of planetary gearbox considering the constraint of ring gear bolt was established. Based on the lumped parameter model, the vibration displacement of each component was solved, and the meshing force of the internal gear pair was calculated. Then the ring gear with bolt constraint was simplified to Euler-Bernoulli beam, and the vibration signal of any point on the ring gear was established by solving the vibration of the beam. Based on the established signal model, the transmission mechanism of vibration signal, amplitude modulation and overlap phenomenon, and the influence of bolt constraint on gearbox vibration were analyzed. Finally, the rationality of the new method was verified by experiments. The new model does not need to consider the window function and weight of the selected vibration components, which can effectively avoid human interference, and has strong universality and applicability.