In order to effectively analyze the influences of parametric uncertainty and correlation on the inherent characteristics of automotive powertrain mounting system (PMS), a method for analyzing the inherent characteristics of PMS is proposed based on the multi-dimensional parallelepiped model, in which both the parametric uncertainty and correlation are considered. In the proposed method, the multi-dimensional parallelepiped model is firstly constructed to describe the PMS parameters with uncertainty and correlation. Then, the uncertain responses of the natural frequency and decoupling rate are calculated by integrating the regulation technique, Taylor series expansion and central difference method. The analysis procedure of the proposed method is presented as well. The numerical results show that the proposed method can deal with the coexistence of correlation and independence of uncertain parameters. Taking Monte Carlo method as a reference method, the proposed method has acceptable computational accuracy, and it can greatly improve the computational efficiency on solving the uncertainty responses of the PMS inherent characteristics. The proposed method and the analysis results can provide important reference for the calculation, evaluation and optimization design of the inherent characteristics of automotive PMS.