Abstract: Numerical simulation was carried out to investigate the influence on film-cooling effectiveness by different structures,and the flow and heat transfer characteristics on endwall of a turbine cascade at different blowing ratios were obtained. The result shows that the jet of column holes produces a pair of coupling counter-rotating vortices at the downstream of cooling holes by the influence of mainstream and cooling jet. The vortices are disadvantageous to the endwall film-cooling. The forward expansion hole reduces the intensity of coupling vortices. The cooling jet is pushed to the wall. These factors make the cooling effectiveness better than the column cooling holes. The forward expansion leakage increases the width of jet,and cools down the endwall between the film-cooling holes. These factors make the forward expansion leakage better than the column holes and forward expansion holes.