In this paper, an active disturbance rejection control (ADRC) system is developed for autonomous quadrotor with obstacle avoidance. In this control system, the controller based on ADRC technique is the main controller. The robust trajectory tracking problem of the quadrotor is solved based on the attitude decoupling control. ADRC attitude decoupling controllers are used to eliminate the effect of the state coupling and uncertainties caused by internal and external disturbances. This control system also contains an avoidance obstacle approach whose trajectories can be obtained through two kinds of potential field with rotation vectors, quadrotor can choose a smoother trajectory from them to avoid the obstacle. The effectiveness of the proposed approach has been verified in simulations.