Graphical Progiamming Platform (GPP) is an integrated software development environment for Virtual Instrument (VI) systems, providing users with a graphically programming way to quickly construct automatic test and measurement systems. VI component library, which is a set of basic cells for building GPP applications with responsibility for data processing functions, is the key part of GPP. In order to achieve high levels of reusability and flexibility, an object-oriented framework for VI component library was presented, described with Unified Modeling Language (UML). This framework make full uses of design patterns and was far more likely to achieve higher levels of reusability and extendibility. Based on such a framework, not only can VI component library reuse both its source code and design architecture, but also can be divelapfd more efficiently and easier to maintain and extend.