In this article, three dimensional (3D) micro CT detection technique was employed to test welds with complex structures. The difficulties of testing the complex structure of welds using conventional radiographic testing were analyzed,thus, 3D micro CT, which provided advantages such as micron order focus size, and high resolution, achieved favorable testing results in electron beam weld, edge weld, and solder joint with complex structures. The results showed that 3D micro CT can realize the three-dimensional testing of complex structure welds. Furthermore, 3D micro CT can identify, locate and measure the holes, cracks, and incomplete penetration, providing foundation of weld quality evaluation.