The tunnel defects were prepared through process tests on 6005A-T6 hollow aluminum profiles, and metallographic,hardness and tensile tests were carried out. After stretching, the fracture was scanned to study the effects of different size defects on the mechanical properties and microstructure of 6005A-T6 hollow aluminum profiles. The test results show that the tensile strength of the joint is negatively correlated with the tunnel size in the thickness direction. The SEM scan results show that there are a large number of equiaxed dimples at the center and edge of the tensile fracture, all of which are ductile fractures; the tunnel defects are all located in the lower part of the weld nugget on the forward side, the weld nugget zone and the vicinity of the tunnel are subjected to strong mechanical stirring, and a dynamic recrystallization process occurs, all of which are fine equiaxed crystals. The microstructure of the heat-affected zone is not much different from that of the base metal, and the grains in these two zones are elongated in the rolling direction of the profile; there are softening zones on the forward and backward sides, and due to heat-mechanical action, the minimum hardness value of the backward side is 63.6 HV, the minimum hardness value of the forward side is 84 HV.