Through the direct parameter approach,a solution for spacecraft attitude tracking is presented.First of all,the spacecraft attitude tracking control model is built up by the error equation of the second-order nonlinear quaternion-based attitude system.Based on the control model,a suitable controller is designed by the direct parameter approach.Compared with other control strategies,the direct parameter approach can offer all degrees of freedom for the controller to satisfy the requirements for system properties and turn the original nonlinear system into closed-loop linear system.Furthermore,this paper optimizes the controller according to the robustness,limitation of controller output and closed-loop eigenvalue sensitivity.Putting the controller into the original system,the state response of the closed-loop system and the output of controller are plotted in Matlab to verify the availability and robustness of the controller.Therefore,the controlled spacecraft can achieve the goal of tracking on the mobile target with the external disturbance torque. Through the direct parameter approach, a solution for spacecraft attitude tracking is presented. First of all, the spacecraft attitude tracking control model is built up by the error equation of the second-order nonlinear quaternion-based attitude system. Based on the control model, a suitable controller is designed by the direct parameter approach. Compared with other control strategies, the direct parameter approach can offer all degrees of freedom for the controller to satisfy the requirements for system properties and turn the original nonlinear system into a closed-loop linear system. Furthermore, this paper optimizes the controller according to the robustness, limitation of controller output and closed-loop eigenvalue sensitivity. Putting the controller into the original system, the state response of the closed-loop system and the output of controller are plotted in Matlab to verify the availability and robustness of the controller. Therefore, the controlled spacecraft can achieve the goal of tr acking on the mobile target with the external disturbance torque.