In order to ensure the long-term reliability of the turbine, the wave conditions should be considered when designing the tidal turbine. A three-bladed horizontal axis turbine with a diameter of 0.9m was used as the benchmark model, and the open source computational fluid dynamics (CFD) library OpenFOAM was used to predict the performance of horizontal axis tidal turbine (HATST) under wave and current conditions. Grid dependence tests were conducted to select the optimal grid number to capture the flow characteristics. As a verification study, the generated wave profile was compared with the results obtained from third-order Stokes wave theory, and it was found that the simulation results were consistent with the theoretical results. The effects of different wave frequencies and heights on the power performance of HATST were studied, and the results indicated that the wave height had a more significant impact on the power performance.