To improve the anti-mechanical performance of the 20 cm diameter ion thruster, the mechanical analysis and experimental verification of its existing structure were carried out. After the grids were handled equivalently, the modal analysis and impact response spectrum analysis of ion thruster were carried out based on finite element analysis. The modal analysis results were validated by the fundamental frequency sweep test. Finally, the impact response of the thruster after adopting the damping structure was simulated and verified by experiments. The obtained results indicate that after the grids assembly being handled equivalently, the analysis results’ difference are about 8.3%-11.9%. The modal analysis result shows that the base frequencies of the thruster in the x, y and z directions are 246, 248 and 336 Hz respectively. The grids and middle magnet pole are the weak links in the mechanics of the ion thruster and affect the overall structural stability. The 1600g response spectrum analysis results indicate that 1600g, the surface stress of the grids concentrates on the rim of the aperture region, furthermore the deformation largely occurs in this region. When the vibration damping effect with the stiffness of 1000 kN/m is taken, the overall deformation of the grids is reduced by 60%-82%. Mechanical test results show that, during the low-frequency scanning process of 10-1200 Hz, the base frequencies of the thruster x, y and z directions are 256, 258 and 348 Hz respectively, basically consistent with the simulation results. Secondly, the 20 cm diameter ion thruster with damping measures passed the 1600 g impact test.