Appliciltion systems focusing class units, as component abstraction based on source code, has insufficient benefit of independency and reuse of elements. Only few effects are acquired, because it is only inclined implementation. We need design pattern to represent not only the problem abstraction but also information and relationship between system elements for generic solutions of specific domain Also, it is essential to software reverse engineering to catch the correct system through examming the cxisting system and utilizing the acquired knowledges as reusable resource. Namely, software reverse engineering for extracting the design pattern is very important because it improves the understand ability for system analysis and design through extracting the design structure of object-oriented system, and provides rich and high leIel reusabilitv through grasping the standard idioms and relationships between components. In this paper, we defined the extraction algorithm for design patterns with standardized, packaged and quantitative measlIIul thruugh applying reyerse engineering into existing ubject Olicnted system. And we designed the reengineering toul including reverse engineering for autumatic extractiun of design patterns ami reuse fur retrieval. editing and rebuilding oi design patterns. Also we applied the algorithms into Java applications.