Abstract: To investigate the cause of bracket fracture during bench testing of a specific expansion tank model and enhance its structural reliability, a finite element model of the expansion tank was built via ANSYS Workbench. Modal analysis and harmonic response analysis were performed to acquire the vibration characteristics of the expansion tank under bench test constraints. The analysis revealed excessive vibration stress at the bolt hole of the No.1 bracket, which exceeded the material yield limit. Structural optimization and simulation analysis were subsequently carried out for this critical region. The results demonstrated that the maximum stress on the optimized expansion tank shell is 3.1 MPa, far lower than the material yield strength of 22 MPa, which proves the effectiveness of the improvement.