Abstract: In recent years, the contradiction between socio-economic development and environmental protection has become increasingly acute. With the increased demand of natural resources, environmental states have undergone significant changes, and even irreversible degradation has occurred. It is a great challenge to effectively utilize resources and ensure human welfare. The Safe and Just Operating Space (SJOS) theoretical framework that has emerged in recent years provides an effective assessment method for sustainable human development to maintain the safe and fair use of natural resources while ensuring the safety of the environment and ecology. This study chosen the Datong Lake catchment in the middle and lower reaches of the Yangtze River to analyze the characteristics of the Environmental Kuznets Curve in the catchment. The SJOS framework of the catchment was constructed from two aspects: social foundation and environmental system. The results showed that the social-ecological system in the Datong Lake catchment can be roughly divided into three stages: the preliminary development stage (1950s—1980s), the degradation stage (1980s—2000s), and the recovery stage (post 2000s). The freshwater use, air quality, and water quality in the catchment have surpassed environmental limits and are in dangerous states. In addition, the two social basic dimensions of poverty eradication and industrial innovation in the river catchment is relatively low. This study provides important information for maintaining regional sustainable development, and is also an effective method for constructing regional SJOS framework.