The work-hardening characteristics and deformation behavior of high deformability pipeline steel with a polygonal ferrite and bainite microstructure were studied in this paper. The high work-hardening ability of polygonal ferrite with 35% bainite (PF+35%B) dual phase sample contributed to its high tensile properties. Electron backscattered diffraction was conducted to analyze the mechanism of the micro-damage behavior. The results of kernel average misorientation and grain reference orientation deviation of the deformation microstructure revealed that the main deformation mechanism of the polygonal ferrite grain was slip with a number of slip systems. Dislocation rearrangement and a local orientation gradient caused by crystal rotation during sliding to cause the formation of micro-voids. The strain dispersion ability of the PF+35%B sample was better than that of the polygonal ferrite with 27% bainite (PF+27%B) dual phase sample. The risk of micro-voids nucleation and crack propagation were reduced to an improved plastic deformation ability for PF+35%B sample. The average Taylor factor (M) of the PF+35%B sample was higher than that of the PF+27%B sample, which indicated the grains of the PF+27%B sample was more liable to slip during deformation and yield under low stress. The evolution characterization of the micro-texture showed that the γ-fiber was more stable compared with the α-fiber, and the stronger γ-fiber may contribute to the improved plasticity.