The Voice Coil Actuator-Fast Steering Mirror （VCA-FSM） driven by Voice Coil Actuator is an important servo mechanism in inter-satellite laser communications. The flexible support structure inside the FSM and the relative motion between the axes cause complex coupling properties in the system and reduce the control performance of the system. For this problem， a two-axis loop shaping $H_{\mathrm{\infty }}$ decoupling control method based on model identification was proposed in this paper. Firstly， the system impulse response sequence was solved based on the excitation and response data， and the system Hankel matrix was constructed for system identification； subsequently， considering the coupling characteristics of the system， a two-axis loop shaping $H_{\mathrm{\infty }}$ robust controller was designed based on the nominal model； finally， step response and sine sweep experiments were carried out based on the VCA-FSM servo control experimental platform. Experimental results show that compared with LQG and LQR control， the two-axis loop shaping $H_{\mathrm{\infty }}$ robust control proposed in this paper increases the X- and Y-axis tracking closed-loop bandwidth of the system by 54.3 Hz and 54.8 Hz respectively， significantly reduces the coupling characteristics of the system. The control method proposed in this paper fully improves the performance of the VCA-FSM servo system and realizes the high-performance decoupled control of the two-axis VCA-FSM.