The system aspect of sustainable development implies concern about a total system composed of the many natural and human subsystems, while the long-term aspect of sustainable development implies concern even about of these systems.Obviously it is a practical impossibility to develop and use an indicators set that include s indicators of sustainability from every system in the total system.Realizing that a drastic restriction to a manageable number of indicators is essential, we face the difficult task of defining a set of indicators that can provide a picture of the sustainability of the total system and essential subsystems.The theory of fundamental orientations of the sustainable development systems produce a train of thought to solve the problem.The basic orientors are to be serve as a checklist to make sure that essential aspects of sustainability are not overlook.Systems must be compatible with their system environment and its characteristic properties in order to be viable and to exist sustainably.The environmental properties can, therefore, be viewed as imposing certain requirements and restrictions on systems, which orient their functions, development and behavior.There are various ways of determining fundamental environmental properties.Six fundamental properties of system environments are found:normal environmental state, resource scarcity, variety, variability, change and other systems.Corresponding to the six fundamental environment properties, there are six environment-determined basic orientors (existence, effectiveness, freedom of action, security, adaptability, and coexistence), plus the system-determined basic orientors (reproduction, psychological needs, and responsibility), these orientors of system and their relationship form the fundamental structure to assess the sustainability of a system.As a minimum, the sustainability of three essential systems would have to be considered corresponding to sustainable development systems:the human system, the support system, and the nature system, furthermore, their individual contribution to sustainability of the total system has to be assessed.Finally, the paper takes Zhangye Prefecture as a case to assess the sustainability of total system from 1978 to 1995.At the same time, summarizes the advantage and disadvantage of the theory of the fundamental orientations of sustainable development systems.