For the attitude control problem of quadrotor affected by external disturbance and modeling uncertainty, an active disturbance rejection attitude control method which consisted of a fixed-time reduced-order extended state observer (RESO) and a fixed-time backstepping state feedback controller was proposed. Based on the quadrotor dynamics model and active disturbance rejection control(ADRC) theory, firstly, a RESO with fixed-time convergence property was designed and the convergence of the observer was proved theoretically. Secondly, a based on the backstepping control theory, a fixed-time backstepping controller was designed combined with the fixed-time control theory, and it was theoretically proved that the tracking error of closed loop system can converge to the origin at fixed time. Finally, the performance of the proposed control algorithm was investigated from the indexes of rise time, steady-state error, maximum error and mean square error through simulation cases. The simulation results demonstrate that the proposed improved method has better control quality compared to the traditional ADRC and backstepping sliding mode control.