Abstract: This paper presents a large eddy simulation (LES) study of turbulent flow structures in a hydro-turbine operating in the rated condition, including the details of the well captured structures and an analysis on the features of vortex cascade and turbulent energy dissipation in blade passages. And survival rates of vortices in different scales and the corresponding energy dissipation are examined. Results show that the survival rates vary significantly over a blade passage and the volume ratio of vortices in two adjacent scales is about 1.2-1.6. The large scale structures in a blade passage feature low survival rates, while the small scale structures have quite high survival rates and dominate along the flow in the passage. Along the flow, turbulent kinetic energy and eddy viscosity are increasing rapidly and the small scale structures keep growing, implying how an energy dissipation channel is formed in the blade passage.