The purpose of this paper is to use the most widely used formal language-VDM ＋ ＋ that has characteristics of accuracy and consistent in describing syntax and semantic of the system model, combined with VDMTOOLS and Rational Rose tool to transform the various elements of the UML class model into representation of VI）M＋ ＋. This method achieves the various elements contained UML class model about the syntax and semantics checking, and further improves the quality of UML modeling.