Abstract: Based on the theory of eco-efficiency, the empirical research on eco-efficiency and its change path of Jiangsu Province from 2005 to 2014 was conducted, and the relationship between the economic development and environmental pressure explored by using the decoupling analysis method. Finally, the gray relational method was used to diagnose the main factors of resource and environmental efficiency which affected the change of eco-efficiency in Jiangsu Province. It was found that from 2005 to 2014, the resource efficiency of all the indexes in Jiangsu Province fluctuated, and most of the environmental efficiency increased slightly. The integrated resource efficiency and environmental efficiency fluctuated, and the environmental efficiency fluctuated more than the integrated resource efficiency. In terms of the eco-efficiency and circular economy model, Jiangsu Province took a leap-based economic development model, and the decoupling status of economic development and environmental pressure was unstable, mainly including three kinds of state, i.e. the strong decoupling, weak decoupling and expansionary recoupling. The gray relational analysis showed that the comprehensive utilization of solid wastes, industrial electricity, living electricity, living energy, domestic sewage and solid waste were the significant contributors to the change of eco-efficiency.