In order to solve the evaluation problem of optical system under partially polarized light conditions caused by single ray tracing method, a full-field, full-pupil ray tracing method based on Stokes notation was proposed. The refractive and reflection Mueller matrix expressions were improved. The analytical relationship among the degrees of polarization(DOP) of the incident light, the ray angle and the DOP of the emitting light was analyzed. The analysis results show that when the difference value between the incident angle and the emergence angle was less than 5.7°, the influence of the system on the DOP of the light can be reduced effectively. According to the space target polarization imaging requirements, a polarization imaging optical system with micro-polarizer array(MPA) was designed. The resolution was 0.5 m at the distance of 500 km. Dynamic data exchange(DDE) was used to trace the full-field and full-pupil rays for the optimized optical system. Four Stokes vectors and full-field polarization distributions were both calculated and displayed. Due to the DOP of any field of view can be calibrated, the polarization detecting accuracy of the optical system was improved. Therefore, the target can be recognized by matching the DOP of the incident light and the DOP of any field of view.