In the optical system of quantum communication optical ground station, two fast control mirrors, corresponding to precision and high-precision tracking, are used to form a single detection mode closed loop. In order to ensure the control accuracy and stability of the system, decoupling must be considered in the control process. However, when the SNR of the target is low, it is difficult to realize the accurate decoupling of precision and high-precision tracking loops. This paper proposes to add a position sensor in precision and high-precision tracking loops, respectively. On the one hand, the position sensor closed-loop is used to improve the certainty of the inner loop control object and facilitate parameter setting. On the other hand, the deviation of the position sensor reflects the deviation of the TV miss distance. The fine tracking adopts the correction of the deviation of the position sensor for closed-loop, so as to avoid system decoupling. This paper analyzes the object characteristics, control system design method, and robustness of the compound axis control structure based on this method. Theoretical and experimental results show that the proposed method has better robustness and higher accuracy without decoupling control when the target characteristics are poor, especially when the delay changes greatly.