A novel highly birefringent photonic crystal fiber (PCF) with elliptical air holes in the fiber cladding and arrays of subwavelength doublehole units with size of about 0.16 μm in the fiber core was proposed. Dispersion and birefringence property of the proposed PCFs was investigated by using a fullvector finiteelement method (FEM) and anisotropic perfectly matched layers. Curves between modal birefringence (confinement loss) of the proposed PCFs and the wavelength of the input light for PCFs with different parameters of ellipticity, normalized area，diameter of the two microholes, distance between the two microholes are reported in details. Simulation results showed that high birefringence (larger than 0.001) and ultralow confinement loss (less than 0.000 2 dB/km) are achieved. The proposed design of the PCF is an approach to achieve both the high birefringence and the low confinement loss by introducing asymmetric microstructure both in the fiber cladding and in the fiber core.