Abstract: By using nonoverlapping domain method,a 3 D viscous code had been developed to calculate flow field in a cascade with tip clearance and craping along casing.A turbine stage of NASA is also simulated.The results show that the relative exit flow angle (and axial flow angle) is reduced by leakage flow on top of the rotor.As a result,the flow angle on top is underturned and its loading is reduced.The shock wave structure on top of the rotor becomes very complex and out of order due to interaction between the leakage flow and the shock wave.This out of order shock wave structure will bring high loss.