Along with the research and application of UML in depth, people in software development have cognized that the semantics of UML mainly described in nature language have some drawbacks such as ambiguity and scarcity of accuracy etc. In this paper, we first summarize the necessary of a kind of formalized semantics and previous studies, then provide some semantics of static modeling elements in UML on principle of conciseness, clarity, intelligibility and practicality from two aspects of extension and intension. Thus we provide an effective method of apprehending these modeling elements in depth quickly and exactly, and a basis for the study the semantics of static diagram, translation between elements and models, and the model extension.