A fault-tolerant control method was proposed based on adaptive control for the quadrotor UAV in the presence of actuator fault and external disturbances.The actuator fault was added to the system model in the form of multiplicative factor, and the attitude was described with unit quaternions.Considering the under-actuated characteristic of position subsystem, the virtual control force was introduced, and the actual thrust and the desired attitude were calculated out.To the position and attitude subsystem with both actuator fault and external disturbances, an adaptive fault tolerant controller was designed to track the desired attitude.Finally, the simulation shows the effectiveness and stability of the proposed controller.