Software reuse includes low-level components reuse, high-level components reuse and system architecture reuse. High-level components reuse and software architecture reuse are still limited to some domain specific models, while low-level components reuse is constrained by machine’s retrieve ability. This paper proposes a mechanism that builds software in three levels, namely software system, high-level components and low-level components. Each level has a unique structure and organization manner. The focus of the paper is on the construction of high-level components and their matching and composition approaches. Design pattern is proposed for building generic high-level components with large number of alternatives. Once a pattern model of high-level component is constructed, it can be directly used or generalized. Design space incorporated with formal specification technology is introduced to not only precisely describe the relationship between high-level components but also easily analyze components matching and composing. The method is illustrated with a debugger example.