The human-land system is a complex and open giant system composed of two subsystems of geographical environment and human activities. Though the optimization of the relationship between two subsystems, we could realize the regional sustainable development. The regional sustainable development is the embodiment of the most optimization of human-land system. This paper revealed human-land system, in terms of connotation, structure, relation, mechanism and function. Based on the theory of human-land system, the paper proposed the regional sustainable development assessment model and carried out the empirical analysis in the township scale. We chose Haiyong Town as the study area. The results show that the study area is in a good level of regional sustainable development, but in a primary stage. The economic sub-system and the society sub-system have reached the good level of sustainable development, but the environment subsystem is always at a low level. The study area should put forward optimization strategies within the economic, social and environmental subsystems, such as ecological agriculture strategy, circular economy strategy, modern service industry strategy, environmental protection system strategy and so on, in order to promoting regional sustainable development. The research results can provide scientific reference for the assessment of regional sustainable development and the formulation of regional sustainable development strategy.