According to the characteristics of the multi-support rotor system, the mechanical model of the multi-support rotor system is established, the effect of torque excitation and coupling stiffness on the multi-support rotor system is considered, the sensitivity equation of the bearing load to torque excitation is derived, the sensitivity matrix of the bearing load to torque excitation is solved, and the transfer characteristics of the transient torque excitation in the multi-support rotor system is simulated. The results show that the bearing loads of each support of the multi-support rotor system change with the effect of transient torque. The bearing load of the multi support rotor system increases as the initial value of the transient torque increases. In addition, the amount of change of the bearing load increases when the support is close to the location of the torque excitation. The phenomenon of a sudden increase of the bearing load appears in positions away from the torque excitation. Finally, the test is set with the same simulation conditions, and the results of the simulation are experimentally verified.