Abstract: In order to obtain optical characteristics of the photonic crystal fiber with double air holes and quadrilateral lattice arrangement, the finite element method was used to simulate the fiber. The results of birefringence, limiting loss, polarization beat length and dispersion characteristics of the fiber were obtained. The results show that, compared with the elliptical air hole photonic crystal fiber with square lattice arrangement, the double air hole photonic crystal fiber with square lattice arrangement can obtain higher birefringence characteristics, reaching 10^-2 orders of magnitude, under the same air duty cycle conditions. The limiting loss difference of the two polarization modes of the fiber can reach 10³ order of magnitude. This type of optical fiber is easy to manufacture, and has a certain application prospect in optical fiber communication and optical fiber sensing.