Abstract: Based on structure characteristics and gray distribution of industry CT image,there are different kinds of artifacts as well as grey with regional property in reconstructive tomography.It's hard to find the segmentation threshold exactly.So a kind of segmentation method was designed for industry CT image.This method can make use of Ostu segmentation method and the method of image process in order to elimitate the outside artifacts,and the center air by approaching clustering.Finally,we can get result of region of interest.The result of algorithm experiment show:This method can pick up region of interest correctly for industry CT image with prior knowledge.