Abstract: The T-type joint of heterogeneous aluminum alloy 5083-O/6082-T6 was subjected to friction stir welding by using different assembly gaps including lap gap, butt gap and misalignment, and the mechanical properties of the welding joint were compared and analyzed. The test results show that when the lap gap, butt gap and misalignment increase within the certain range, the tensile and shear properties of the T-joint do not fluctuate significantly, and the bending performance decreases. The lap gap is controlled at 0.6 mm, the butt gap is 1.2 mm, and the misalignment is 0.6 mm, the T-joint is in good shape, no tunnel, hole and other defects are found, and the wall plate and rib plates are effectively connected, which can be used as the key control point for the T-joint to implement friction stir welding in engineering application.