Abstract: A dual-loop attitude tracking robust controller was presented for rigid spacecraft to deal with the attitude tracking control problem. Attitude dynamic equation was decomposed to two independent subsystems by presetting a bounded virtual angular velocity. The preset virtual angular velocity in outside loop was used to ensure the attitude asymptotical converge to desired attitude,and was taken as a virtual input of inner loop subsystem. The uncertainty composed of rotational inertia perturbation, external disturbance and exceed saturated amplitude could be estimated by second-order differential observer accurately. Then,an observation value based attitude controller was designed to make the real angular velocity exponential converge to virtual angular velocity. Analysis results show that, the dual-loop attitude tracking controller can satisfy the constraints of bounded angular velocity and control saturation,present higher tracking accuracy and robustness.Numerical simulation results validate the robustness and effectiveness of the dual-loop attitude tracking controller.