Abstract: UIMS (User Interface Management System) is a package of software tools which support the implementation, debugging and evaluation of interactive human- computer dialogues for reducing the design cost of interactive systems and improving the friendliness of user interfaces. One of the key issues is to specify and organize the user interaction sequences. The specification languages used to describe man-machine dialogue proposed recently have their limitations. This paper presents a specification language UISL (User Interface Specification Language) based on ATN (Augmented Transition Network) and module structure to counteract the weaknesses of languages proposed and acquire complete, concise description of user interfaces.