Abstract: Aiming at part of the old Francis turbines are not matched with the latest runner,formulate the transformation and comparison scheme,the hydraulic characteristic model of the flow passage of Francis turbine is established according to the Reynolds averaged N-S equation and standard k-ε equation through local transformation and optimization and set the boundary conditions of the runner. The velocity and pressure distribution of movable guide vane（fixed guide vane）and inner runner in the transformation scheme were obtained based on CFD three-dimensional simulation. The flow field of each scheme under different working conditions was compared and analyzed to predict turbine performance and put forward optimization suggestions. The engineering example indicates that the efficiency of the turbine increases6%～8% and the output increases 2%～3%. The internal flow characteristics and the operation stability of the turbine are improved,the degree of cavitation erosion of the flow parts is reduced. The research results have a certain reference for the transformation of the similar turbine.