Abstract: In order to realize the efficient and accurate detection of laser welds of aviation lithium battery, a multi-channel multi-frequency eddy current detection system with the function of tomographic imaging was designed and developed. The system and the 5-channel anti-interference differential structure eddy current sensor were used to detect the typical defects in the tab polar plate weld, such as local incomplete welding, overall missing welding, weld deformation and concave, and micro defect. Based on the principle of skin effect, tomographic imaging technology was used to scan and image the overlap. The results show that the developed multi-channel multi-frequency eddy current detection system with the function of tomographic imaging can effectively detect a variety of typical defects in the tab polar plate weld of lithium batteries, and the smallest defects can be detected at \phi 1 mm. The tomographic imaging technology enables the observation of defect morphology at different depths. Through the comparative analysis of a large number of test results, the identification methods of defect type, location and length were summarized, and a set of defect identification process and evaluation criteria were proposed, which laid a good foundation for the engineering realization of the lithium battery weld detection.