Abstract: In the real ocean environment, the tidal current turbine will encounter active or passive yaw operation, and thus the hydrodynamic performance and wake field characteristics of the turbine will change greatly under yaw condition. To fully explore the variation rule, the non-yaw CFD numerical simulation of tidal current turbine is firstly carried out in this paper, and its accuracy is verified by a model test. Then, the hydrodynamic performance and wake field characteristics of the tidal current turbine under the yaw angle of 0~45° are studied. The results show that the decreasing trend of turbine power and axial thrust load is accelerated with the increase of the yaw angle, and the instantaneous fluctuation of power is much larger than that of axial thrust load. In the range of 0~45°, the cosine rule has a better prediction effect on the power decline than the axial thrust load decline, but it overestimates both of them, and the prediction deviation increases first and then decreases. After 30°, the lateral deflection distance of the wake will not continue to increase. The cross-section distribution of the yaw wake is kidney-shaped, counter-rotating vortex pairs with upper and lower distribution exist, and the maximum velocity deficit region is located in the upper region of the kidney-shaped distribution.The research results have reference significance for the operation control and array layout of tidal current turbines under active or passive yaw conditions.