Abstract: The flow field structure of a film cooled turbine for a typical design with four rows of cooling holes on the suction surface has been investigated in a plane cascade rig by the aid of flow visualization techniques and pneumatic probe measurement.The experimental results showed that a little vortex in opposite direction of rotation emerged as the passage vortex existed at the root of suction surface.The vortex was induced mainly by mixing between mainstream and injecting air,and resulted from formation of kidney-shaped vortex.The injected air was essentially absent in a triangular region extending from near the region of peak curvature on the blade to its trailing edge,and the separation line of the passage vortex was skewed toward the end wall.A very complex three-dimensional flow occurred in the downstream of the jet exit,and remained near the blade surface at the exit of the cascade.The kidney-shaped vortex was kept near the blade surface,and mixed with the wake at the exit of the cascade.