Abstract: For improving the design speed and accuracy, we proposed a numerical model of optimal design for torsional vibration damper in engine shafting based on sensitivity analysis. Firstly by investigation on relationship between design parameter of torsional vibration damper and vibration character, a method of optimal design for torsional vibration damper was discussed. Then through sensitivity analyzing and design variables choosing, optimal design was carried out. At last, the validity and correctness of the model was verified by comparing the above results and experience calculation results. The optimal resonance peak was shifted to higher frequency direction and the resonant amplitude was smaller than that of experience calculation results, which showed precision and accuracy of the optimal design method.