Abstract: A hybrid active disturbance rejection control (ADRC) scheme for stable loop was proposed. In order to make the semi-strapdown seekers have strong robustness under the coupling disturbances induced by disturbance torques and scale error and other uncertain perturbations. Firstly, the mathematic model of the semi-strapdown stable platform was established. Secondly, a hybrid ADRC system for the stable platform of a semi-strapdown seeker was designed. The influence of controller parameters on the control performance was analyzed by studying the frequency characteristics of ADRC, and the design principle of control parameters was given. Finally, the hybrid ADRC scheme was verified by mathematical simulation. The simulation results show that, compared with the traditional controller, the hybrid ADRC achieves better control accuracy and can effectively overcome the influence of disturbance torque and scale error on the seeker. The amplitude of the disturbance rejection rate (DRR) can be reduced by about 67.9% under the typical attitude disturbance frequency(2 Hz). The research results can provide guidance for the design of semi-strapdown seeker stable control system.