The three-dimensional geometric model of the fringe-beam frame had been built based on the frame structure of a light truck. In order to optimize the frame structure, the finite element model of the frame and the suspension system were set up. Considering the influence of suspension on frame dynamic performance, the modal properties of the frame model was analyzed in the commercial analysis program ANSYS, using two different methods. Based on the experiments, it was verified that combining MPC184 elements and spring elements Combinl4 is a better way to simulate suspension compared to using spring finite elements only. Furthermore, the combined simulation results coincide with experimental modal analysis results, which were conducted thereafter. Subsequently, the frame stress-strain distribution rules and dynamics response were calculated under the random road spectrum excitation, and the frame dynamic parameters were obtained. This study provides some theoretical bases for frame structure improvement, and proposes an optimum method to simulate suspension. The results have direct significance in ensuring the stability, comfort and reliability of a light truck frame.