Abstract: Durability is a research hotspot in the field of vehicles. The physical fatigue test on vehicles is costly and time-consuming. In order to shorten the development cycle and reduce research costs, a virtual test method was proposed to study the durability of vehicles. Firstly, a finite element model was established for a research object of a large special freight vehicle, and the results of stress distribution and frame deformation were obtained through static analysis; the modal information of the flexible body structure was obtained through modal analysis. And then, based on the modal stress recovery theory, considering the flexible body of the frame, upper swing arm, lower swing arm and force axis, a rigid-flexible coupling model of the whole vehicle was established, and the dynamic response of driving on a flat road was obtained. Compared with experiment results, the root mean square value of the vertical acceleration at the measuring point of the frame is in acceptable range, validating the correctness of the model. Finally, according to the Palmgren-Miner criterion, the driving life of the vehicle was evaluated on grade D roads. The results show that the fatigue life of the 4 axle suspension structure is the smallest, and the lower swing arm structure has obvious stress concentration. An improved lower swing arm structure can increase its service life, providing a reference for the design of vehicle structure.