Abstract: China's industrialization and urbanization levels have increased rapidly in the 21st century, but the rough economic growth model has brought many ecological and environmental problems. In recent years, 26 counties in the mountainous areas of Zhejiang Province have formed a new mode of realizing common wealth by green development, and improving eco-efficiency is an important way to promote the realization of green common wealth. By constructing an eco-efficiency evaluation system and using Super-SBM, kernel density estimation, and Tobit model, we analyze the characteristics of spatial and temporal evolution of eco-efficiency in 26 counties in mountainous areas of Zhejiang Province from 2005 to 2021 and the influencing factors, and summarize the paths of eco-efficiency improvement. The results show that: The eco-efficiency of the 26 counties in the mountainous areas improved significantly during the study period, but the degree of improvement varied among counties, and there were fluctuations in the process, which led to diversified types of changes; Spatially, the ecological efficiency of eastern counties is higher, while that of central and western counties is lower; The eco-efficiency was affected by the economic density, industrial structure and other factors, and there are differences in the degree of significance of the influencing factors. Finally, it summarizes the various paths to improve eco-efficiency, such as economic agglomeration and industrial undertaking, and proposes countermeasures to improve regional eco-efficiency by exerting economic radiation and ecological spillover effects.