Abstract: The paper studies the representation and reuse of scheme design knowledge, and presents a knowledge reuse method based on extenics and case-based reasoning (CBR). In these methods, matter-element model in extenics is firstly applied in CBR to represent the cases and the problems, qualitatively and quantificationally. Distance from a point to an interval is presented to calculate the correlation from the case to the target interval. The optimal matched design case is achieved by adopting the correlation-based retrieving in cases. Methods of extension transformation are finally used in the case adaptation to fit the selected case into the target requirements. An example of turbine selection design is provided to examine the algorithm.