A Fractional-Order Model Reference Adaptive Control (FO-MRAC) strategy based on PD control is proposed to realize attitude control of quadrotor UAVs,which is affected by undervoltage batteries and variation of rotational inertia.Firstly,by analyzing the nonlinear motion equation of a UAV with motor module,a control model containing uncertain time-varying factors is constructed.Then,three attitude control laws are designed for the pitch,roll and yaw channels respectively.The stability of the system is proved by Lyapunov theorem.Finally,comparative simulation experiments with the traditional PD control and the ordinary MRAC are designed,which illustrate the superiority of the proposed method.The method can effectively eliminate errors,improve dynamic performance and stability of the system.