The high-temperature deformation mechanism of oxide scale on low micro-alloy carbon steel was studied using a thermo-mechanical simulator. The thickness, cross-sectional morphology, element distribution and grain structure of oxide scale were observed by electron probe microanalysis (EPMA) and electron backscatter diffraction (EBSD). The results indicated that the plasticity of oxide scale depended on temperature and degree of deformation. Furthermore, FeO layer was the primary region where plastic deformation distributed. This can be explained by the grain structure of FeO layer consisted of loose and larger columnar grains which was beneficial to the plastic deformation. Therefore, the oxide scale and steel substrate at high-temperature developed in equal proportion according to the plastic deformation mechanism of oxide scale, which revealed that the surface quality of hot-rolled steel could be improved by the hot-rolled process.