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A structure was designed to reduce the pressure fluctuation in the draft tube by axial water jet. And the water was obtained from the spiral case through the runner cone into the draft tube. Pressure fluctuation model test of the Francis turbine with and without axial water jet was carried on. And the pressure pulsation amplitude and frequency characteristics with and without axial water jet at four part loads were analyzed. The mitigation effect of pressure fluctuation with axial water jet was studied. It was shown that at part load operation there was a vortex rope in the draft tube and the frequency of the rope was about 1/5 rotating frequency. This vortex rope caused strong low frequency pressure fluctuation. It was the main reason for the unsteady operation of the turbine. With axial water jet the amplitude of the low frequency pressure fluctuation was significantly reduced, but the frequency was not changed obviously. Axial water jet made the vortex move downstream and played an inhibitory effect of the double-vortex.