Until now software development has been developed through analysis, design, and implementation from scratch by software developers. Therefore, many efforts and costs are required to develop software, and the quality of developed software does not satisfy customer`s requirements. In order to address these problems, software development paradigm is shifting in component-based software development, and the effort of applying design patterns into software design is increasing. Proven various design patterns have been introduced by [Gof95], [Grand98], and etc. However, there are few concrete guidelines for how to apply design patterns into design phase in software development or component development of specific business domain. This paper proposes techniques of extracting and applying design patterns needed design phase in component development. In case study, we identify and apply design patterns into EC(Electronic Commerce) component design and development. By applying design patterns, component design`s reliability and availability as well as reusability can be improved.