Using finite element method, thermal stress characteristics and birefringence of stress-induced and modal fields of polarization-maintaining optical fiber (PMF) with bow-tie shape and elliptical cladding shape are analyzed. Stress and birefringence distribution of PMF are gave. Variation laws of fiber-core birefringence and mode birefringence with inner radii of stress regions to bow-tie shape PMF are demonstrated, and variation laws of fiber-core birefringence and mode birefringence with change of elliptical ratio of elliptical cladding PMF arc demonstrated. The effects of the stress domain structure of the fiber on stress birefringence and modal birefringence are investigated and compared .