Watershed management is changing from single factor management of environment and resources to aquatic ecological protection integrated management. Water resources carrying capacity and water environment carrying capacity have not fully adapted to this situation. Therefore, it is necessary to build a new carrying capacity theory to solve the current aquatic problems. According to the demands of watershed water ecological integrity protection management, based on water ecological carrying capacity concept model, water ecological carrying capacity concept, which reveals its basic connotation of “partition, staging” property and "quantity, quality, order" progressive comprehensive constraint effects, was put forward in this paper. Then the paper analyzed its key optimal regulation variables, and established the water ecological carrying capacity partition coupling concept model using eco-regions as elements. Considering the communication of water flow and water quality among eco-regions, the system dynamics simulation model of Taizi River basin water ecological carrying capacity was established, the water ecological carrying capacity of 8 eco-regions were simulated, and optional regulation schemes of each eco-regions were determined， which can provide a scientific basis for the sustainable development of the watershed.