This paper in order to investigate the crack and fracture problems of a truck frame fixed structure. Taking a urea tank bracket as the research object, the fatigue reliability of the bracket is evaluated by the fatigue damage results obtained by the random vibration fatigue simulation method. Firstly, the finite element model of the urea tank bracket was built, and the modal analysis and frequency response analysis were carried out. Taking the power spectral density (PSD) converted from the acceleration signal of the bracket collected in the experiment as the load excitation, the fatigue simulation analysis of the structure was carried out. The fatigue damage results of the urea tank bracket were obtained. The risk position of the simulation results was basically consistent with the bracket fracture position feed backed by the market, which verifies the accuracy of the simulation method. Structural improvement to the risk location, the fatigue damage results of the improved structure was significantly reduced compared with damage results of the original structure, which verified the rationality and effectiveness of the simulation method, and also provided a reference for the subsequent development and design of similar structures.