In this paper, a systematic investigation of equal channel angular extrusion/Pressing (ECAE, ECAP) process on the AZ31 alloy and die design is performed by using numerical simulation. The stress distributions on the die were obtained, and general consideration of the die during the whole pressing process was given. The numerical results revealed that effective stress distribution at the corner of the cavity and the extruded load during extrusion processes was effect by channel angles and friction factor. From the simulations, it was found that the closer the die corner is, the higher stress value results can be acquired. And the effective stress concentration in ECAP die cavity corner. The extruding load fell rapidly when the angular angle increasing. With the increase of friction factor, extruding load also increased significantly. The proposed method can serve as preconditions to analyze the abrasion and fatigue of ECA Pressing die. Besides, this method also provides a feasible way for other die stress analysis.