<p>A Duffing oscillator model was developed to characterize the torsional vibration behavior of the rolling mill transmission system under two excitation frequencies. Solving the model with the perturbation method showed that the system’s response frequencies are linear combinations of the excitation frequencies, with amplitudes depending on these combinations. The study further explored the impact of response and fluctuating rolling force frequencies, revealing that certain frequency components from the transmission system have minimal influence on the vertical vibration system through the deformation zone, as confirmed by field experiments. To mitigate vibrations, a suppression method was proposed, adding a filter to the frequency converter output to attenuate specific harmonic currents. The method was successfully applied in the field, with combined torsional and vertical vibration monitoring confirming its effectiveness.</p>