Polarization properties and propagation characteristics of polymer photonic crystal fibers (PCFs) with elliptical air-holes and hexagonal structure are investigated by using the full vectorial plane wave method. The results show that the birefringence of the fiber is induced by asymmetries of the cladding. The modal birefringence of a PCF is 5.312×10－2 at the elliptical ratio η=3.0. The numerical results show that the modal birefringence of PCF is three orders of magnitude higher than the conventional polarization-maintaining fibers (PMFs). Moreover, by adjusting the elliptical ratio of cladding, we find the optimized design parameters of the fiber with birefringence. Zero walk-off point occurs at a wavelength longer than that of convention elliptical PMF. With increasing elliptical ratio, the walk-off curve and zero walk-off point would shift towards the long wavelength region. The occurrence of zero walk-off point can efficiently restrain the first-order polarization mode dispersion.