星间激光通信中，由粗跟踪系统和精跟踪系统组成的复合轴系统完成了系统的大范围、高精度跟踪任务。对复合轴系统进行了基于Z变换的数字模拟以研究其带宽设计。根据计算的卫星轨迹和粗跟踪系统机械误差，得到了粗跟踪系统的带宽设计结果；给出了粗跟踪系统和精跟踪系统的配合工作关系；得到了精跟踪系统的带宽设计结果；最后研究了在中高频扰动下，复合轴系统的带宽设计。以上结果为星间激光通信中的复合轴系统控制系统设计提供了重要依据。

In space laser communication, the composite axis system (CAS), consisting of the coarse tracking system (CTS) and the fine tracking system (FTS), accomplishs the wide ranging and high accurate tracking tasks. The digital simulation of CAS based on Z transform is given to study the bandwidth design of the CAS. According to the trajectory of the satellite and the mechanical error of the CTS, the bandwidth design of CTS is obtained. Moreover, the cooperation of CTS and FTS is given, and the bandwidth design of FTS is gained. At last, the bandwidth design of CAS with disturbance of medium and high frequency is presented. The results above present the theoretical basis for the design of CAS control system.