Rock CT is a hot topic of research in the field of rock mechanics.Rock CT images can intuitively gives all information in the sections of rock.The extraction of crack and cavity information from rock CT images is most important to the intensive study of rupture mechanism of rock.A rock CT image processing program was developed wtih VC++,the importantcharacteristics of information were extracted from rock CT images by using VC++ digital image processing technology,this provide the information upon which to base studying microscopic damage evolution of rock.