In this paper we propose a novel octagonal birefringent photonic crystal fiber，which shows birefringence when the size of several holes near the core is enlarged. The modal field，dispersion，confinement loss，birefringence of the fiber fundamental mode and the influence on birefringence of some parameters are simulated by multipole method. The dispersion，confinement loss，birefringence of the hexagonal photonic crystal fiber having the same parameters were also computed. By comparision，we conclude that the octagonal photonic crystal fiber have larger birefringence，smaller confinement loss and shorter wavelength of zero dispersion than the hexagonal photonic crystal fiber with the same parameters.