Water function regionalization (WFR) is the basis of water resources management and the total amount of water pollutant control. Taking county as the lest unit, according to chosen social economic indicators,the paper used hierarchical clustering method to class every county in Poyang Lake basin. By using hierarchical clustering method, the counties within Poyang Lake basin were clustered according to the socio-economic conditions. And then, the WFR partition principle of Poyang Lake watershed was formulated by reference to social and economic conditions and current WFR status. From the results of hierarchical clustering, WFR map of Poyang Lake watershed was generated and the dominant water functions of each county were determined. From the water function regionalization map, agriculture water dominates the water function in Poyang Lake watershed, the industrial water regions mainly locate in the northern of Jiangxi province, and fishery water regions mainly distribute around the Poyang Lake. Therefore, the regionalization result thought the advantages of watershed and region management of water resources and could better fit the situation of region management of water resources, and can provide a scientific basis for the reasonable development and sustainable utilization of water resources in Poyang Lake watershed.