A kind of highly birefringent quinquangular-core photonic crystal fiber (Q-PCF) structure is proposed and analyzed by full-vector finite element method (FEM). The modal field, effective index, and birefringence properties are investigated. From the numerical results, it is found that the birefringence of the new polarization-maintaining PCFs is at least five times larger than that of the standard highly birefringent hexagonal PCFs (H-PCFs) with the same hole pitch, hole diameter, and whole hole area as that of the new PCFs at 1 550 nm. Moreover, the modal field of the new PCFs could be better restricted than that of the standard highly birefringent H-PCFs; hence, the loss of fibers could be reduced.