Due to the wide range of speeds of the vehicle engine, the resonance cannot be completely avoided. Aiming at this problem, the analysis of the dynamic characteristics of the vehicle transmission system is transferred from the analysis of the intrinsic characteristics to the analysis of the dynamic response, and the sensitivity analysis based on the dynamic response is derived. This study investigates dynamic response sensitivity to model parameters in a nonlinear single-stage planetary gear set coupled with lateral and torsional directions. The equations of response sensitivity are deduced with the direct method (DM) and the root mean square (RMS) method. Gear meshing is a main reason for gear vibration, so gear meshing power sensitivity to model parameters is analyzed in this paper. Also the influence of rotation speed is considered in the response sensitivity. The sensitivity characteristics make it possible to provide support for dynamic design optimization.