To simulate the hydrodynamic performance of a floating current turbine in combined wave and flow environment is important. In this paper, the ANSYS-CFX softwareis used to analyse the hydrodynamic performance of a vertical-axis turbine with various influence factors such as tip speed ratio, pitching frequency and amplitude. The time-varying curves of thrust and lateral forces are fitted with the least square method; the added mass and damping coefficients are refined to analyse the influences of the former factors. The simulation results demonstrate that, compared with the non-pitching and rotating turbines under constant inflow, the time-varying load of rotating turbines with pitching exhibit an additional fluctuation. The pitching motion of the turbine has a positive effect on the power output. The fluctuation amplitudes of thrust and lateral force’s envelope curves have a positive correlation with the frequency and amplitude of the pitching motion and tip speed ratio, which is harmful to the turbine structural strength. The mean values of the forces are slightly affected by pitching frequencies and amplitudes,but positively proportional to the tip speed ratio of turbine. Based upon the least square method, the thrust and lateral force coefficients can be divided into three components, uniform load coefficient, added mass and damping coefficients, and the middle one is significantly smaller than other two.Damping force plays a more important role in the fluctuation of loads induced by pitching motion. These results can facilitate the study of the motion response of floating vertical-axis tidal current turbine system in waves.