Abstract: There is obvious vibration in the medium pressure feed water piping of a 650MW nuclear power unit. Through on-site investigation, measurement and analysis, this paper expounds the causes and mechanism of vibration in the medium pressure feed water piping, the influencing factors of vibration and the technical method of piping vibration isolation. It is considered that the main cause of piping vibration is the lack of rigid constraints and damping in the horizontal direction of pipeline system, and the horizontal stiffness of pipeline system design is low. In addition, abnormal state of piping supports and hangers will also aggravate piping vibration. Based on the modal analysis and stress calculation of pipe system, the technical scheme of pipeline vibration isolation is formulated. After implementation, the pipeline vibration isolation effect is good, the vibration is significantly reduced, and the stress of pipe system is qualified. Vibration of Piping elimination achieving the desired result．