As a field of research in software engineering, software Re-Engineering has started to attract wide attention in recent years.The key to the Re-Engineering activity is the ability to recover "lost" or otherwise unavailable information from the information available in the existing software source code.This paper introduces SAIS, An Integrated Rule-based System for Analysis of Software Sructure, which is designed to provide partially support to software maintenance and reverse-engineering activitie.The design,implementation,application and features of SAIS are bre briefly described in the paper.