Microstructure evolution and mechanical properties of AZ31 Mg alloy during equal channel angular extrusion (ECAE) at the temperature range of 453-498K was investigated. The processing temperature is an important factor to affect the microstructure and mechanical properties of the Mg alloy during ECAE. ECAE processing can be practiced at 498k or upon the temperature for as-received AZ31 alloy. A new two-step ECAEed processing was successfully used with lowing the processing temperature to 453k. The ductility increased but yield stress decreased though the grain refinement after ECAE at 498k because the recrystallization took place and large angle grain boundary formed. However both the ductility and yield stress were increased after two-step ECAE, which was ascribed to grain refinement as well as incomplete dynamic recovery and recrystallization during the processing.