The hydraulic suspension system is an important system of modular assembled trailer, which is used to turn trailer, control chassis frame height and make trailer comfortable. Therefore, the parts durability of suspension system has been required for service life and safety starting in design. Durability analysis on the parts of hydraulic suspension system is performed in this paper, including linear static analysis and fatigue life analysis. The vibration characteristics of finite element model are determined, which is verified by vibration measuring experiment. The fatigue life of suspension system parts is calculated by stress-life method with the effects of the road roughness and trailer speeds are considered.