Abstract: Effects of welding speed and rotational speed on the formation and mechanical properties of the welded joint of 30 mmthick 5083 alluminum alloy by friction stir welding were studied.Resultsshowed the forming quality and tensile property of weld can reach that of base metal when the optimum range of friction stir welding process parameter was obtained for 5083 aluminum alloy with thickness of 30 mm. were excellent when the rotational speed was within 400~600 r/min and the welding speed 80 ~120 mm/min.