Abstract: This paper presents a prediction method of the fluctuation amplitude of pressure in Francis turbine draft tubes, using data conversion into two parameters: relative discharge to a zero-swirl unit discharge, and dimensionless pressure fluctuation amplitude relative to the velocity head at the runner blade outlet. We conducted a qualitative analysis on the velocity triangle at the runner outlet and compared this new method with the norm-recommended method in terms of pressure fluctuation in the draft tube cone of a Francis turbine. Then, the method was applied to the models of 12 power plants and their homologous prototypes, and comparison of the calculations gives a satisfactory similarity between the model and homologous prototype. Further, we compared the predictions with field test results and obtained a good agreement between them. Thus, our conversion method is effective and feasible for analysis of pressure fluctuations.