A new method of repeated upsetting-extrusion (RUE) deformation was presented. The effects of different deformation temperatures on the microstructure and texture of RUE deformed AZ31 magnesium (Mg) alloy were studied using optical microscopy (OM), X-ray diffraction (XRD), electron backscatter diffraction (EBSD), and Vickers hardness tester. The results show that the microstructure of the AZ31 Mg alloy is locally refined to 0.8 μm after RUE deformation, and the main refinement mechanism is the continuous dynamic recrystallization (CDRX). As the temperature increases, the texture of basal plane parallel to shearing plane is formed firstly, followed by texture with weaker intensity, and finally and textures. The texture split is caused by the dislocation slip of basal áa？ and pyramidal áa？. The maximum hardness of the AZ31 Mg alloy after RUE deformation is increased by 42.4% compared with that at the initial state, which is mainly due to the fine-grained strengthening and the dislocation strengthening.