Abstract: A variety of tools support the description of SA（software architecture）, this makes it difficult for the designer to choose a suitable tool because they are not only domain specified, but also different in description method. A core model of SA is presented which includes the common characteristics of SA. It provides a foundation for tools of ADLs （architecture description languages）, that’s to say, if a tool is chosen to describe SA, only the corresponding constraints are to be added. Manwhile, UML （unified modeling language） and SA are combined to describe software architecture through multi view based on the extension mechanism of UML. Finally, an example implemented in the Rational Rose98 is given.