Abstract: Meso-crack of concrete in CT image is the key object to study.It’s very difficult to observe directly meso-crack of concrete in CT image based on grey scale conception.Image enhancement processing method is needed to CT image according to subtraction conception.Subtraction CT image has some shadow-positive circle phenomenon.So before subtraction operation, CT image is needed to correct.Correction methods including whole translation, whole geometric and region of interest correction method, while region of interest correction method is objective.This paper proposes a new useful method to gain meso-crack information of concrete in CT image.