Adaptation knowledge is usually the most important and difficult stage in building a case-based intelligent system. Existing intelligent systems for hydraulic system design use production rules as its source of knowledge. However, this leads to problems of knowledge acquisition for case adaptation and knowledge base maintenance. This paper describes the application of CBR to hydraulic circuit design for production machines, which helps acquiring adaptation knowledge and solving problems by reusing this acquired knowledge (experience). A technique Case-Based Adaptation (CBA) is implemented in the adaptation stage of CBR so that adaptation becomes much easier. The details of CBA and its implementation are discussed. A prototype system has been developed to verify the usefulness of CBR in hydraulic power machine design.