Abstract: Software Understanding is always the bottle-neck problem in maintainance,It is time consuming and boring.With the development of the Micro Electronic material technique,IC-CAD software become more huge and complex,which makes it more difficult to understand them.The tool in this paper,ICSUT(IC-CAD Software Understanding Tool),aims at helping engineers to understand IC-CAD software.Here the program understanding task is supported with multiple views concerning different levels of attributes of the program.