In this paper, depending on the analysis of internal mechanism, motivity, patterns and process of regional development in a system point of view, definition of regional sustainable development, extensive entropy and hypothesis of information dynamics were established. Region is a terrain of earth surface with a relative stability, where human being deals with its social and economic activities. The definition of regional sustainable development can be expressed as follows:For a special region, sustainable development is a process that will not destroy the capacity of satisfying the needs of citizens in this region at both present and in the future. In the system point of view, region is a complex gargantuan system in the opening and dynamic evolution condition. In fact, the process of regional sustainable development is that the regional structure with an evolutional order in time and space is being established continually by fluctuation mechanism. The evolutional order in time and space in a region may be described by the concept of extensive entropy, and the concept is corresponding to extensive information. The regional sustainable development is a process with quantity accumulation and quality elevation of information, and decrease of extensive entropy. In theory, component Logistic curve may be the best pattern for regional sustainable development process.