Abstract: Creation is an essential nature of Artificial Intelligence and is a challenge to AI on the design research.This paper analyzes characteristics of the creative design and describes in detail the decomposition-synthesis application in the case-based reasoning creative design.The case is represented by snippets that are linked orderly and can be retrieved directly and sequentially.While fulfilling the design by synthesizing snippets from more than one case,it brings the new variables or schemes into the target space of the design.Therefore,it is proven that the decomposition-synthesis is one of the effective methods in creative design.