The internal and external surface, exterior angle, welding seam and tensile fracture surface of 5B01 aluminum alloy square tube are investigated by means of macrostructure, scanning electron microscopy and fracture morphology observation, and the extrusion temperature effect on the quality of profile extrusion is studied. The results reveal that the internal and external surface are in good quality and the exterior angle achieves good welding results without any fracture at 430 ℃ extrusion treatment, meanwhile it has good plasticity, shows ductile fracture, and its tension strength, yield strength and elongation rate are 335 MPa, 138 MPa and 26% respectively.