Abstract:After the overhaul of Unit 2 of Ge Li Qiao Hydropower Station, the swing of the lower guide bearing is found to be too large when it starts. When the vibration exceeds the permissible value, it will affect the power quality, safe operation and lifespan of the unit. It is necessary to find out why and reduce or eliminate it. Concerning the specific condition of Unit 2 of Ge Li Qiao Hydropower Station，the paper discuss factors that may affect the vibration of the hydro-generator unit ，and analyze and eliminate those one by one through experiments,including rotation speed changes ， excitation changes and dynamic balance. Through the above efforts, the problem of the large swing value of the lower bearing is solved ,and also the inadequate oil basin structure is found to have a continuous increase effect on the swing of the lower guide bearing. Analysis and treatment in this paper is mainly based on dynamic balance experiment and mechanical components checking，which provides references for other similar power plant units to deal with the problem of large swing value.