Abstract: Aiming at the insufficient stiffness of the bonnet polishing system of the six-degree-of-freedom tandem joint robot, which may cause vibration and further mid-spatial-frequency errors, used we the IRB 6700 robot as the research object, established the modal analysis model based on Ansys Workbench and combined experiment to analyze the dynamic characteristics of the robot bonnet polishing system in the working condition frequency range. The experimental and simulation results together show that the robot bonnet polishing system has at least 5 modes in the working condition frequency range, and the jitter amplitude at the end of the robot is millimeter-level when the resonance occurs. Robot processing is severely restricted. In addition, for the application of advanced optical component polishing technology in the robotic bonnet polishing system, a vibration suppression bonnet tool was designed, and the fixed-point polishing and whole-surface polishing comparison experiments were carried out with the ordinary bonnet tool. The results show that the RMS and spectral amplitude of the fixed-point polishing spot of the vibration suppression bonnet are generally lower than that of the ordinary bonnet, and the introduced mid-spatial-frequency errors PSD is 40% lower than that of general bonnet polishing.