Abstract: An online indirect measurement method for pitching and yawing moments of a wind or tidal current turbine is provided. The method uses an online indirect measurement system including an incoming flow velocity measurement module, a generator rotation speed measurement module, a pitch angle measurement module, and a computer; the incoming flow velocity measurement module measures the flow velocity of the rotor center; the generator rotation speed measurement module measures the generator rotation speed; the pitch angle measurement module measures the pitch angle of each blade; the computer receives signals of flow velocity, generator rotation speed, and pitch angle, obtains the pitching moment and yawing moments of the turbine via an online calculation, and displays and stores the measured and calculated data in real time.