Abstract: The auxiliary feedwater turbine driven pump is one of the engineered safety features of nuclear power plant,which can supply water to the steam generator of the secondary circuit in a passive way under extreme conditions. The vibration of the pipeline of the auxiliary feedwater turbine driven pump in a nuclear power plant was found first time in China. Based on the analysis of the abnormal vibration mechanism of the steam auxiliary pump pipeline,a hypothesis of causing pipeline vibration was put forward. The hypothesis was verified by data test and analysis,the finite element simulation and experimental study. After the corresponding improvement measures were put forward,the problem of abnormal pipeline vibration was completely solved.