Abstract: To investigate the cause of bracket fracture during bench testing of a specific expansion tank model and enhance its structural reliability, modal analysis and harmonic response analysis were performed using ANSYS software. The vibration characteristics of the expansion tank under bench test constraints were obtained. The analysis revealed excessive vibration-induced stress exceeding the material yield limit at the bolt hole of the primary support bracket. Structural optimization and simulation analysis were subsequently conducted for this critical area. Results demonstrate that the maximum stress on the optimized expansion tank shell is 3.1 MPa, significantly lower than the material’s yield strength of 22 MPa, thereby meeting the structural strength design requirements.