Abstract: Sustainable development can be summarized as the establishment and development of the coordinated relationship among population, resources, environments and development. Excessive population growth, lack of natural resources, aggravated environment problems have seriously hampered the sustainable development of human society of the 21st century. In this thesis, the author thinks that the main problem of the sustainable development and the coordinated relationship is the unbalanced distribution of population, resources, environments and development in the material world, while the unbalanced development of human society intensifies the unbalanced distribution of the material world, therefore, it brings about the uncoordinated relatonship under the unbalanced conditions. Besides the controlling of excessive growth of population, the key point to resolve this problem is to promote the all-round development of human society, especially to quicken the development of the developing countries and strengthen the reasonable flow of population, energy, material and information, so that it can establish a scientific intelligent adjusting system.Geography always takes the coordinated relationship among population, resources, environments and development, that is, the relationship between the development of human society and geography conditions as one of the most concerned study fields. Facing the sustainable development problems which the whole world concerns, geography must unify the regional difference law with the material unbalanced distribution law, and reveal the movement developing law of the coordinated relationship among population, resources, environments and development by the space system which is consisted of flow, network and boundry line, and take the construction of flow-geographic construction as a stage where it will serve the sustainable development of human society, so geography will serve the sustainable development of human society, and achieve a revolutionized development.