Abstract: A 3D hydrodynamic model based on Flow-3D is developed in this paper for single pile horizontal-axis tidal stream turbine and the influences of the blade pitch angle on the impeller rotation rate, the impeller kinetic energy, the fluid force, the water level and the flow velocity of the horizontal-axis tidal stream turbine are investigated by the model. Numerical analysis results showed that: when the blade pitch angle increases, the fluid force on the impeller in the direction of the incoming flow and the impeller kinetic energy increases; the pitch angle has little effect on the impeller force perpendicular to the incoming flow direction; the larger the blade pitch angle is, the flow velocity in the downstream of the turbine declines more quickly and the flow velocity is smaller; in far downstream of the turbine, the larger the blade pitch angle is, the faster the wake field recovers and the larger the flow velocity is.