Abstract: In order to solve the problem of large error in the existing casting internal defect detection methods, a casting internal defect detection method combined with rigid elastic image registration technology was proposed in this paper. Firstly, the rigid registration combined with Demons elastic registration was used to realize the registration of the spatial position of the casting ones to be tested and the template image. Secondly, the subtraction ones of the image to be tested and the template image were obtained through the digital subtraction technology. Then the false defects caused by the registration error were removed by the threshold segmentation method. Finally, the position of the defects in the defect image to be tested was determined and marked. Experimental results showed that this method could accurately realize image registration and accurately detect the defects of the image to be tested.