The Luanhe River Basin is an important ecological security area in China. It is urgent to carry out assessment of water ecological carrying capacity and identify the limiting factors of bearing capacity to guide the construction of ecological civilization in the basin. Based on the integrity of water ecosystem service function, this paper constructs the capacity assessment and indicator contribution quantification method from the four dimensions of “water resources-water environment-water ecology-water safety” using the WaREES framework, and carries out the application of Luanhe River Basin assessment based on the survey. The results show that the hydro-ecological carrying capacity index(HECCI) of the Luanhe River Basin is between 43.8 and 53.8, indicating the overall a critical overload situation. The special assessment showed that the water environment was in a safely loaded state (61.3), both water safety and water ecology were critically overloaded, while water resources were overloaded (22.9). The weak endowment of water resources and the high development intensity are the key shortcomings that limit the carrying capacity of the basin. The contribution rates of water resources endowment and water use index to the basin HECCI are 6.4% and 5.5%, respectively. Aquatic habitat quality, biological integrity and hydrological regulation are the main controlling factors for the critical carrying of water ecology and water safety. The proposed water ecological capacity assessment technology method is scientific and practical, and has reference value for watershed/regional water ecological environment management.