High temperature deformation behavior of AZ31 Mg alloy was investigated in this study on the basis of a processing map (e » 0.6). To construct a processing map, compression tests were carried out at various temperatures and strain rates. Two regions of high deformation efficiency (h) were identified as: (1) a dynamic recrystalization (DRX) domain at 250°C and 1/s and (2) a superplasticity domain at 450°C and 10-4/s. The average grain size observed in the DRX region was considerably smaller (2.9µm) than in any other region. In the superplastic condition, tensile elongation to failure approached to 1040%. At the high Z regions, flow softening occurred resulting from the dynamic recrystallization but below 1010 of Z value, flow hardening occurred due to the grain growth. Possible deformation mechanisms operating at high temperature were discussed in relation to the activation energy. A two-stage deformation method was found to be effective in enhancing the superplasticity of AZ31 Mg alloy.