In order to produce fiber-optic polarization components and devices, a simple scheme is proposed for a birefringence holey fiber to improve dispersion characteristics of its polarization beat-length. The cross-section of the birefringence holey fiber with circular micro-holes cladding array and a pair of large holes near the cores is squeezed or expanded in orthogonal directions. To deduce the wavelength sensitivity of polarization beat-length, compensation and equilibrium are made among the birefringence dispersion curves with opposite signs induced by multiple asymmetric structures. The influence of different structural parameters on the modal birefringence is calculated and analyzed through full wave beam propagation method. By optimization to the structural parameters, a flatten dispersion curve of polarization beat length is obtained in 1550 nm wavelength windows with the central beat-length value around 39.5 mm. The relative variation of beat-length is 1.27% in wavelength range 1380~1750 nm. If this fiber is made into zero-order quarter wave plate in 1550 nm wavelength window, the operation wavelength band is about 1400~1710 nm under the retardation tolerance of 2π/300 and the relative bandwidth is up to 20%.