The structural vibration caused by poor rigidity is one of the main obstacles limiting the machining efficiency of robot milling. The existing vibration suppression strategies mainly focus on process parameter optimization, passive vibration absorption at the end and feedback control of joint motor. Although these strategies have certain vibration suppression effects, they cannot directly improve the structural rigidity of the robot. In this paper, a joint wearable structural reinforcing device (JWSRD) is proposed, which can achieve vibration suppression effect by improving the rigidity of the robot joints, fundamentally improve the processing ability of the robot, and ensure the processing stability. Firstly, the structure of the device is designed without affecting the processing flexibility. Secondly, the braking torque of the JWSRD is tested. Considering the feedback of joint braking torque, the vibration simulation model under harmonic excitation is derived. Finally, the offset mass experiments are carried out to verify the vibration suppression effect of the JWSRD. The results show that the JWSRD installed on the robot joint has the notable potential to enhance the structural rigidity, reduce the machining vibration and improve the machining efficiency.