Stray light simulation and analysis is one of the key means to ensure high-accuracy polarization radiation data of the directional polarization camera. According to the structural and operating principle of optical system, the dominated resource of the stray light is analyzed. For the difficulty of applying point-source transmittance method to analyze stray light in large field optical system, method for analysis of stray light based on the principle of black spot is presented. Instrumental three-dimensional geometry model and optical property are established by software of LightTools. The influence of stray light inside and outside the field-of-view of optical-mechanical system is simulated respectively by means of selected field point backward tracing. The result shows that the effect of stray light mainly comes from inside the field-of-view, and on-axis field is influenced mostly. The stray light coefficient is 3.27% which satisfies the requirement of design index. In addition, global stray light and local stray light are simulated by on-axis and real ray forward tracing which provides a theoretical basis and guidance for subsequent image stray light correction.