In this paper, prediction of the shaft power is studied. The slip factor and the leakage flow factor used for the performance calculation are obtained experimentaly. The method of prediction of the shaft power is based on the angular momentum theory, and it is derived from measurement of the slip factor, blockage factor and leakage flow. The slip factor is strongly related to the blade angle β₂, the number of blades Z and the capacity coefficient φ, and it is smaller than 0.35 at 170 degree of β₂, which is much smaller than that for the backward blades. The difference between the calculated values and the experimental results on the shaft power is 5 % for the range of φ less than 0.3 and is 11 % for φ= 0.45.