Ducted contra-rotating rotors UAVs (ducted UAVs) flying in confined space are subject to turbulent inflow that induces unsteady moment force on the UAV body. This phenomenon leads to poor robustness and low control accuracy of the attitude control system. This work is concerned with the development of an improved Active Disturbance Rejection Control (ADRC) method to overcome this problem. First, the kinematic and dynamic models suitable for an in-house ducted UAV are developed. Based on these models, a method combining PID and ADRC is developed and employed for attitude control of the ducted UAV. Real flight test of the ducted UAV shows that that the designed attitude control system exhibits good robustness and disturbance rejection performance.