Abstract: The distributions of metal flow rate along different extrusion directions and the pressure of welding room during hot extrusion of 6063 aluminum alloy profile were studied by HyperXtrude software. The reasons of size deviation were analysed and restrictive blockings were used to optimize the extrusion die. The simulation results show that the flow rates of metal in different directions was slow down after adding restrictive blockings, especially inward direction, so restrictive blockings could decrease the size deviation of the profiles.After the optimization method was applyed to pratical extrusion process, it was found that the uniformity of flow rates of metal were improved and the qualified aluminum alloy profiles could be obtained.