Reusing software architecture and its constituents, which are a kind of coarse-grained software resources, are confronted with great difficulty. Reflection mechanism has been successfully applied in the reuse of code component, but scarcely applied in the reuse of architecture and its constituents. Architectural reflection is the computation performed by a system about its own architecture, and currently confined in the realm of the runtime management and dynamic evolution of software systems. This paper proposes a reflection mechanism supporting the reuse of architectural level design, which offers the information support for reusing the architecture and its constituents at design time of software architecture by modeling the meta-information about the base-level to construct a meta-level architecture. Moreover, this paper illustrates the approach to describing meta-level architecture of this reflection mechanism, and presents the solution of constructing this reflection mechanism in detail. Through this reflection mechanism, architects could accomplish the tasks of architecture design efficiently at software design stage, by reusing software architecture and its constituents.