Abstract: In order to inspect and image the weld defects with different orientation in aluminum alloy sheet, the feasibility of pulsed eddy current thermography (ECPT) is investigated. Based on the Maxwell's equations, Joule's laws and heat conduction equation, the fundamental principle of ECPT for aluminum alloy is analyzed. Based the testing principle, the ECPT system is built for the weld defects with different orientations. Experimental results show that the proposed ECPT system can effectively detect the defects with different orientations in aluminum alloy sheet. The maximum thermal response increases with the increase of the defect orientation, and finally stabilizes. The excitation current density and the excitation duration has little influence on the response. The study provides an alternative for the weld defects of aluminum alloy.