Interactive tabletops and surfaces (ITS) are important components in computer supported co-located cooperation environments. ITS is different from the traditional WIMP interfaces and has the features of horizontal display, multiple input devices, and single display groupware. There is a lack of guidance in the development and design of ITS. A user interface model is proposed to solve the problem. First, a description method is proposed to describe multiple devices and the collaboration interaction, which adopts part of the methodology Penichet chosess to analyze person-computer-person interaction and also proposes an additional task-devices table (TDT) to ease the description of the interaction of different devices in ITS. Next, the ITS user interface metaphor OCAL (Objects Containers Adorners Languages) is described. Based on the analysis, Puerta's general computational framework is specific into ITSUIM (Interactive Tabletops and Surfaces User Interface Model) under the guide of OCAL. Finally, an application example is given. Experimental results show that the method proposed here is capable of being efficient enough to support the design and development of the user interfaces of ITS.