A design of polarization-maintaining retro-reflectors (PMRRs) for folded-path applications is proposed and analyzed. The prism-based scheme enables the output light, which is parallel to the input, to have an identical state of polarization. The principle of the design is theoretically verified, and the related error is analyzed due to possible manufacturing imperfection. The maximum spatial angle error is +-2.75o. The effect on the extinction ratio and insertion loss is also discussed, which further proves the design's feasibility in practical applications.