Abstract: The coordinated development of water resources and social economy is of great significance to promoting ecological environment protection and regional comprehensive high-quality development. Taking Zunyi City, a typical mountainous city in Southwest China as the research object, we constructed a comprehensive index system for the coordinated development of the two systems, analyzed the coordinated development status and interaction mechanism of ‘water resources-social economy’ in Zunyi City from 2009 to 2019 by using entropy weight method and coupling coordination model, and explored the influence mechanism of the coordinated development of the two systems combing with grey correlation coefficient. The results showed that: ① During the study period, the comprehensive level of water resources first decreased and then stabilized, indicating that the water resources carrying capacity and efficiency first decreased and then stabilized, while the overall level of socio-economic development showed an upward trend. ② The coupling coordination state between the two systems had changed from barely coordinated (0.596) in 2009 to moderately coordinated (0.719) in 2019. ③ The difference of coupling coordination degree between water resources and social economy development was affected by economic and technological development, industrial water utilization structure, urbanization construction, water resources endowment, water environment governance level and other factors, which made the two systems influence each other in the development process and evolve in coordination. The study can provide a scientific reference for the optimization and sustainable development of water resources in mountainous areas of Southwest China.