Abstract: The extrusion process of an aluminum alloy bar with diameter of 22.5mm was simulated based on Deform-3D software. The effects of the thickness of die bearing and the depth of flow-guiding hole on metal flow behavior, extrusion load, temperature and die stress were analyzed. The results show that surface quality of extruded bar is getting better as the thickness of die bearing increasing from 1.3 mm to 1.7 mm under the same extrusion condition, however the extrusion load rises by 30 kN and the outlet temperature increases by 7 ℃ simultaneously. As the depth of flow-guiding hole increases from 10 mm to 20 mm the extrusion load increases by 90 kN and the outlet temperature rises to 553 ℃ which exceeds the extrusion temperature limit.