since the X8 rotor UAV provides control redundancy, we can take advantage of this characteristic to make the X8 rotor UAV stably fly, when the UAV is damaged. There are many methods to achieve this goal. The most common method is the pseudo inverse method. However, the pseudo inverse method does not consider the existence of the position limits of actuators, the pseudo inverse method may cause the actuator to advance into saturation. To solve this problem, this paper puts forward a method using kernel space to adjust the result of the pseudo inverse method. The method realizes the X8 rotor UAV to get the maximum lift in the case of faults and avoids the motor advancing into the saturated state. In this paper, we use an X8 rotor UAV to verify the theory mentioned above, the result shows that compared with the pseudo inverse method, this method can effectively improve the thrust weight ratio, achieving the desired objectives.