Abstract: The transmission system of cross-country crane construction machinery is taken as the research object in this article. Based on the analysis of vehicle transmission system composition and working principle, the discrete vibration model of crane front-end transmission system is established. The modal frequency of the system is solved by analytical method. At the same time, the time domain characteristics of the torsional vibration of the Wilson-theta system are calculated and analyzed, thus the torsional vibration law of the crane transmission system at any speed is obtained. This study provides theoretical guidance for low vibration design of the drive system of cross-country lifting construction machinery.