During the overhaul of unit 4 of a nuclear power plant, one heat exchange tube was found to be broken during the pressure inspection of the low-pressure heater. Further eddy current inspection was carried out for the rest of the heat exchange tubes of the low-pressure heater. A total of one sunken tube and six worn tubes were found, and the damaged parts were all located at the support plate. In view of this problem, this paper analyzes the manufacturing quality, corrosion and flow field of the heat exchange tube, focusing on the vibration characteristics of the heat exchange tube. It is found that the damaged heat exchange tubes are located in the turbulent flow field area of the low-pressure heater shell, and there are periodic pulse power and local vortex vibration, which cause fretting wear of the heat exchange tube and the support plate hole. It is recommended to measure the wall thickness of the heat exchange tube of the low-pressure heater regularly. If the wall thickness of the heat exchange tube is too thin, the tube plugging measures should be taken immediately.