Abstract: In order to achieve the automatic extraction of spatial position data for bulk defects in I style weldments,automatic corresponding criterion of bulk defects was put forward on the basis of defects segmentation and thinning,and the factors which can influence the automatic corresponding judgement were also discussed.Automatic extraction of spatial position data for bulk defects was carried out by using the provided criterion,and the experimental results of provided method was compared with those of manual labour corresponding.The comparing results show that the above two methods match well basicallly.However,detection efficiency of the former one is improved greatly,and the labour intensity of detection personnel is alleviated greatly as well.This can provide better basis for quick nondestructive testing and joint integrity evaluation of I style weldments.