In software engineering, an architecture description language (ADL) is intended to aid designers in defining software architectures in terms of abstractions that they find useful, and in making a smooth transition to code. Based on ADL, the concept and models of the Virtual instrument system Software architecture Description Language (VSDL) is provided in this paper. The VSDL put forward provides a new method for virtual instrument system's application design and development by describing the virtual instrument system software architecture effectively. In this paper, the model description?component description and line description are analyzed in detail, and the structure language based on the model is also provided. VSDL provides a smooth interface to graphic software platform, and has been applied to many virtual instrument systems' integration and already yielded good results both in technology and economy.