透射比是评价格兰泰勒棱镜性能优劣的一个重要指标，分析了偏振干涉成像光谱仪中重要偏光部件即格兰泰勒棱镜的分光机理，运用光线追迹方法，推导出了晶体光轴不平行时棱镜透射比精确理论计算公式；通过计算机模拟对其传输特性进行了详尽分析，得出了系统透射比随晶体光轴倾斜角和波长变化的关系曲线；给出了在满足系统透射比条件下格兰泰勒棱镜晶体光轴误差被限定的有效区间范围。这一结论为偏振干涉成像光谱仪的优化设计提供了理论指导和技术支持。

The transmittance of Glan- Taylor prism (GTP) is a vital index to evaluate the component′s performance. Glan- Taylor prism is the key component of the polarization interference imaging spectrometer (PIIS). We adopt the Raying tracing method to deduce the theoretical transmittance expression of the GTP. By performing the computer simulation, some important relationship curves are obtained with the variations of the transmittance on optical axis and wavelength. The allowed range of the departure angles for the optical axis in the principle section are calculated. The results provide a theoretical guidance for the study and engineering of the polarization interference imaging spectrometer.