Abstract: The Laser beam welding for 3.3 mm thick 6A02 aluminium alloy plates was implemented, and the effects of hot isostatic pressing process on microstructure and defects of the welded T-joints were systematically studied. The results show that the microstructure of the base metal consisted of α(Al) solid solution and Mg2Si phase and the welding seam consisted of dendrites. The porosity and microstructure defect vanished, the weld center hardness decreased and the base metal hardness increased after proper hot isostatic pressing technology. Contrarily, high hot isostatic pressing pressure and temperature would lead to the appearance of burnt structure and reduce the microhardness of the joints.