为了精确测量航天器对接过程中最终逼近段航天器间的滚转角，设计了基于方波磁光调制的滚转角测量系统。利用法拉第磁致旋光效应并结合马吕斯定律，建立了方波磁光调制后输出信号的模型; 通过分析输出信号的特点，推导了输出信号与滚转角之间的关系方程; 利用滚转角变化过程中输出信号的增减性组合去除了方程的增根，最终得到了基于方波磁光调制的滚转角测量模型。仿真结果表明：文中提出的方法理论测量精度高，可测量-90～90°间的滚转角，优于传统方法。此外，利用方波信号调制具有数据采集简单、信号处理难度低等优势，是实现高精度大范围测量航天器间滚转角的一种新方案。

To measure the roll angle between two spacecrafts at the last-phase of spacecraft-docking accurately, a roll angle measurement system based on square wave magneto-optic modulation was present. A model of the modulated signal was present according to the Faraday effect and Malous law, and the relationship equation between the modulated signal and the roll angle was established according to the character of modulated signal. The combination of the variation trend of the modulated signal was used to delete the extraneous roots of the equation, then the roll angle measurement model based on square wave magneto-optic modulation was acquired. Simulation results indicate that the new method has higher measurement precision, and the measurement scale is -90~90°, wider than that of the traditional method. Furthermore, the new method shows advantage on data acquisition and data process.In conclusion,the method can provide a new reference for measuring the roll angle between spacecrafts in higher precision and wider scale for spacecraft docking.