The basic method of 3-D steady turbulent flow simulation in the inner of Francis runner is introduced in this paper.Finite volume in the body-fitted coordination method and k-εmodel were applied to simulate the 3-D flow in the runner of Fengman Hydropower Station unit 7.The cut-off amount of railing edges of the runner blades were determined

therefore the output power was increased.It proved a new and effective way for old unit to increase its output.