Taking a six-rotor UAV as the controlled object, and considering the shortcoming of the classical control allocation method that the motor speed command value will become saturate when the control input value is too large, we propose an improved scheme for control allocation according to the weights. The weight coefficient is updated in real time according to the changes of the control input value to avoid saturation of motor speed. The simulation results show that, the proposed method can improve the rationality of allocation, reduce the coupling of each channel, enhance the anti-saturation capability of the six-rotor UAV effectively, and improve the flight performance of the UAV.