A rectangular lattice micro-structure optical fiber with a pair of large circular holes near the core is squeezed or expanded in orthogonal directions. Nonlinear variation of birefringence with wavelength is suppressed by the compensation and equilibrium among the birefringence of multiple asymmetric structures. The influence of lateral deformation on modal birefringence and polarization beat length dispersion is analyzed by full-vector finite-difference beam propagation method. A suitable expansion factor is found by optimizing the design. The wavelength sensitivity of polarization beat length is effectively reduced. The polarization beat length changes in the range of 90.7~95.3 mm and the relative variation is about 5% in the wavelength range of 1.0~2.0 μm. This fiber is very suitable for making wideband fiber-optic quarter wave plate.