Abstract: The motor vibration of several large vertical pump units in a nuclear power plant exceeded the standard due to structural resonance, vibration control was carried out through dynamic balance, support adjustment, torque adjustment, etc. The vibration reduction effect was poor and the vibration occurred repeatedly. In view of the limitations of the traditional treatment for structural resonance, and in combination with the operation characteristics of the nuclear power unit, the tuned mass damping technique was adopted for vibration control of the pump unit. After on-site mapping, model design, strength check, simulation analysis, production test and on-site verification, the vibration reduction effect is significant, and the on-site implementation is convenient, without changing the equipment. Through the introduction of this case, a new reference method is provided for vibration control of the rotating machinery.