As a complex underactuated system, quadrotor UAVs demand controllers with exceptional disturbance rejection capabilities to address stability challenges under external perturbations. To resolve the stable control problem under external disturbances, this study proposes an enhanced sliding mode-based active disturbance rejection control (ADRC) strategy. First, a dual-loop control structure is constructed for the nonlinear multi-input multi-output system of the quadrotor UAV, enabling simultaneous closed-loop regulation of position and attitude dynamics. Subsequently, the improved sliding mode ADRC methodology is systematically integrated into the dual-loop framework to develop a robust trajectory tracking control system, which demonstrates enhanced adaptability through its self-tuning disturbance estimation mechanism. Finally, comprehensive simulation validations confirm that the proposed controller effectively suppresses the adverse effects of external uncertainties and disturbances, exhibiting superior robustness and tracking accuracy compared to conventional approaches. These findings highlight the controller’s potential for real-world deployment in dynamically challenging environments.