With the development of the society and economy, the contradictions among population, resources and environment are increasingly worse. As a result, the capacity of resources and environment becomes one of the focal issues for many countries and regions. Through investigating and analyzing the present situation and the existing problems of resources and environment in Poyang Lake Eco-economic Zone, seven factors were chosen as the evaluation criterion layer, namely, land resources, water resources, biological resources, mineral resources, ecological-geological environment, water environment and atmospheric environment. Based on the single factor evaluation results and with the county as the evaluation unit, the comprehensive capacity of resources and environment was evaluated by using the state space method in Poyang Lake Eco-economic Zone. The results showed that it boasted abundant biological resources, quality atmosphere and water environment, and relatively stable geological environment, while restricted by land resource, water resource and mineral resource. Currently, although the comprehensive capacity of the resources and environments in Poyang Lake Eco-economic Zone was not overloaded as a whole, it has been the case in some counties/districts. State space model, with clear indication and high accuracy, could serve as another approach to evaluating comprehensive capacity of regional resources and environment.