A sandwich bulkhead structure has a large volume. Because infrared non-destructive testing technology can only detect a small area, hundreds of tests are required to detect the sandwich bottom structure, which is not conducive to determining the location of defects in a single project. This article proposes a fixed overlapping-area infrared image stitching method in which the overlapping area is fused using weighted fusion to effectively eliminate seams. The six sub-regions on the side of the sandwich bottom structure are stitched using an arc-shaped method. This approach not only solves the problem of stitching in multiple projects but also greatly improves the accuracy and efficiency of defect detection. After collecting and annotating the defects in the project, the stitched image directly displays the location information of the defects, which greatly facilitates the identification of defect information in the sandwich bulkhead structure.