In this paper, an ultra-fine grained AZ31 magnesium alloy sheet with grain size less than 3μm was generated by three-run accumulative roll bonding of as cast alloy at a deformation temperature of 350°C and a reduction of 80% for each pass. The microstructures on the different ARB stages were observed and superplasticity examination in the ultrafine grained AZ31 alloy were carried out at a fixed temperature of 300°C and varied strain rate ranging from 10-4 to 10-1 s-1. It is indicated that significant grain refinement was mainly achieved in the first run and gradual uniformity of grain size in the next by continuous dynamic recrystalization. Besides, a superplastic deformation with a moderate elongation-to-fracture of 316% was obtained at a strain rate of 10-2 s-1 indicating a low temperature and high strain rate superplasticity, while a maximum elongation-to-fracture of 562% at10-4 s-1. The strain rate sensitivity exponent as high as of 0.34-0.41 implies the dominant role of grain boundary sliding in superplastic deformation at strain rate ranging from 10-3 to 10-2 s-1. The results indicate a possible approach to produce magnesium alloy sheet with fine grain and excellent deep drawing workability.