Abstract: The single-polarization single-mode (SPSM) micro-structure polymer optical fiber (MPOF) was designed based on polymethyl methacrylate (PMMA). A full vector finite element method together with beam propagation method was adopted to study the SPSM properties. By optimal designing, we found that only one polarization state of the fundamental mode could be transmitted within the visible light region from 0.52 m to 0.63 m according to the different cutoff wavelengths of the two orthogonal polarization modes. For MPOF with 11 rings of hexagonally arrayed air-holes, the confinement loss of 1.13 dB/m was obtained at 0.57 m. This low loss SPSM-MPOF can greatly eliminate the polarization crosstalk and polarization mode dispersion.