Abstract: he Maxwell equations for the propagation of electromagnetic waves in photonic crystal fibers are solved with plane wave method. The cross section of the photonic crystal fiber is taken as a big unit cell and an infinite twodimensional periodic system is generated, thus the core is regarded as a defect in photonic crystal. The properties of a new model of high birefringence photonic crystal fibers (PCB) and that of dispersion flattened PCB are studied respectively with the supercell model described above. It is found that birefringence in the model is higher than that in conventional fibers when the diameter of the holes in the same line with the core varies. Moreover, in the new model of dispersion flattened PCB, a zero dispersion flattened fiber can be obtained when the diameter of the holes closest to the core takes a specific value. The new dispersion flattened PCB will have great potential in optical communication systems.