Abstract: In order to improve the flight stability, robustness and control accuracy of the quadrotor UAV, attitude control is divided into two control loops, namely, angle loop and angular rate loop. For attitude angle and angular rate, PID controller and LQR controller are designed respectively to form double closed-loop attitude control. Considering the external uncertainties and internal modeling errors of the quadrotor during flight, a first-order linear extended state observer (LESO) is added to the attitude rate loop to observe and compensate the external and internal disturbances in real time. The effectiveness and robustness of the proposed algorithm are verified by simulation and experimental comparison.