Multi-loaded operation is always a feature of marine equipment. Experiments were done on marine centrifugal pumps to study the influence of the shifting-load. Variation of parameters related to rotation speed and flow rate was analyzed. Results of experiments confirmed the empirical formula of the rotation speed against vibration. It was concluded that the vibration level of the centrifugal pump is proportional to the forth to ninth power of the rotation speed. Changing of flow rate has a greater influence on low and high frequency vibration than that on intermediate frequency vibration. The influence even becomes much larger at the characteristic frequency of blades of the centrifugal pump. The general conclusion is that when low flow rate operation condition is required, the rotation speed of the pump should be lowered to reduce the operation noise instead of adjusting the valve of the pump.