[Objective] Coupling development between the natural ecosystem and the social economy system in the mountainous area of the Southern Ningxia Hui Autonomous Region was studied in order to provide a scientific basis for its sustainable development.[Methods] The mountainous area of Southern Ningxia was chosen as the research area, and an index system for the natural ecosystem and the social economy system was constructed using basic ecological and economic indicators for the region. Then the entropy method was used to determine the weight of each index, and this weight was used to calculate the comprehensive development index of the natural ecosystem and the social economy system. The model of coupling degree and the model of coupling harmony was used to analyze the coupling coordination state and the variation trend between the natural ecosystem and the social economy system.[Results] ① During 2000-2017, the level of social and economic development of each county increased gradually, and the comprehensive development index of the natural ecosystem showed a fluctuating downward trend. ② The coupling degree of the study area showed an initial rising trend that subsequently decreased slightly. However, the overall range remained at 0.89-1.00, which was a high level. ③ The coupling coordination degree of the mountainous area of Southern Ningxia belonged to the coordinated development type. From 2015 to 2017, the degree of coordination in Yanchi County decreased, while the degree of coordination in Tongxin County increased slightly, and the degree of coordination of other counties maintained an upward trend.[Conclusion] With the increase in economic level in recent years, the contradiction between ecology and economy has gradually been revealed because the carrying capacity of the ecological environment in the mountainous area of Southern Ningxia has gradually been unable to adapt to the rapid development of the social economy. The model of coupling coordination degree can well reflect the development process of the interactive stress between the ecological environment and the social economy in the mountainous area of Southern Ningxia, thereby providing the basis for correctly understanding the coupling development law for the ecological and economic systems.