Abstract: Vibration problem have been existed on multiple safety injection and spray pumps in the safety systems in many nuclear power plants. Firstly, the vibration condition has been introduced, and the vibration characteristics have been summarized. Spectrum analysis has been implemented. The possible factors related to the fault have been investigated. Secondly, based on the vibration characteristics and frequency spectrum characteristics, a vibration mechanics model is set up. The root cause of excessive vibration is resonance in the system that is consisted of equipment and basement, not the soft feet. It has been validated in the test. Finally, the treatment suggestion of stiffness optimization has been proposed. It was advised that the modal analysis of integral equipment and basement system should be carried out in design phase.