Abstract: The concept and application of on-line supervision technology and corresponding system was booming for recent decades, however, there was no overall top-level design for on-line supervision even though it has been researched and applied for a long time. In this paper, we offered a novel and necessary top-level design for overall on-line supervision system, including the structure, the layer and the function, which would possibly bridge scientific research with technology management. A three-layer design with seven sections at top layer was brought up. The design of top layer was conceived of seven separate yet connected sections, including terminology and definition, general specification, measurement system application, measurement model, method and link, information exchange and inter-operation, acceptance and assessment and reliability. Contents, roles and ranges of different sections were demonstrated in detail while logical relationships, supports and connections between these sections were also carefully illustrated. Admittedly, the top layer was focus of the whole top-level design, functions and utility of the second and the third layer was also specifically introduced.