Aiming at the uncertainty of quad-rotor aircraft model and its sensitivity to external disturbances, a Reduced-order Active Disturbance Rejection Control (RADRC) method is designed to control its position and attitude, and the stability of the control system is analyzed. In this method, the Reduced-order Linear ADRC (RLADRC) is combined with nonlinear tracking differentiator to meet the different requirements of each channel of the quad-rotor aircraft on control performance.Among them, the Reduced-order Linear Expansion State Observer (RLESO) only observes the system output differential signals and disturbances, avoiding repeated observations of known information, so that the system bandwidth can guarantee the estimation accuracy of RLESO, and reduce the noise sensitivity of the system. The trajectory tracking ability and anti-disturbance performance of RADRC are compared with that of the traditional LADRC method through simulation and Qball2 platform experiments, which verifies the effectiveness and superiority of RADRC method.