Grain size refinement by using equal channel angular Extrusion (ECAE) is an effective way to improve workability and strength of the magnesium alloys. Round workpieces of ECAE processes for AZ31 magnesium alloy are investigated by using numerical simulations and experimental studies in this paper. The processing of ECAE is simulated in order to study the influence of the processing on the deformation behavior of the workpiece and extruding load. The variation trends of the effective strain distributions in the workpiece are changed little for different cross-section. Punch load for extrusion is the major factor to be considered while designing a sound ECAE die. The deformation mechanism of ECAE for grain refinement is obtained. In addition, the experimental finally workpieces shapes and extruding load results are also consistent with FE analysis results.