Grain refinement processing by severe deformation, combined equal-channel angular extrusion (ECAE) processing and conventional tube extrusion, is applied to AZ31 magnesium alloy. By a combination of ECAE processing and tube extrusion, a fabricated tube, with outer and inner diameters of 2 mm and 1 mm, respectively, has fine, homogeneous, and equiaxed grain structure with an average grain size of 1.5m. Tensile test results indicate that the fine-grained tubes exhibited a superplasticity potential m value of 0.55.The maximum elongation (688%) is obtained at a temperature of 673K. Furthermore, the tubes fabricated by combined ECAE/extrusion process is applied to dieless drawing process without using any tool and die.As a result, dieless drawing limit is enhanced due to high m value achieved by combined ECAE/Extrusion process. From these results, the effectiveness of new grain refinement processing for fabricating fine-grained tubes and its application for dieless drawing process to fabricate the fine tubes was demonstrated experimentally.