Abstract: A method for the performance prediction of axial-flow turbines with bowed and conventional vanes is presented,which uses flow function as control equation on S2 surface. Profile loss is calculated by numerical method on several S1 flow surfaces. Secondary loss and tip-leadage loss are empirically estimated with pitch-wide average losses along the cascade blades.The effect of the blade bowed angle on the secondary loss is taken into account.The comparison of the predicted results with experimental data confirms the feasibility of the method.