Aimed at the singlespan rotor lateral vibration in the nonlinear response of torque excitation, when torque excitation created at a singlespan rotor frequency, differential equations of motion were established. In respectively rotor system has or no excitation torque, two operating states of equations were simulated and solved, and which results were analyzed by using EMD method. The results show that: lateral vibration signal contains multiple associated with the excitation frequency vibration signal in the torque excitation; and energy diversion is occurred, which has major impact on the stability of the system. Finally, the test platform with the same conditions as a simulation model is established, which test results verify the correctness of the numerical simulation. Besides there exists misalignment fault component in decomposition results in test, and it is discovered that in the presence of faults, torque excitation to make the rotor torque lateral vibration greater.