Abstract: It is important to study water ecological security for integrated basin management. In the present study, the niche theory was creatively adopted to assess water ecological security. Traditional niche theory was improved based on the concept of degree of membership. Dezhou, Lucheng and Xinxiang in different reaches of the Zhangweinan Canal River Basin were chosen as typical cities. The pressure-state-response concept model was used to establish an indicator system for assessment of water ecological security. Subsequently, the degree of membership, niche width and niche overlap of 12 water ecological security indicators were calculated to identify the priority regulation area. The results showed that the niche widths of Lucheng, Xinxiang and Dezhou were 1.332,1.441 and 1.289, respectively, indicating that Xinxiang is the best, while Dezhou is the worst, when evaluated by such indicators. The niche overlaps of Lucheng, Xinxiang and Dezhou were 2.097,2.285 and 2.318, respectively, indicating that Dezhou has a similar resource utilization pattern as Xinxiang, which suggests that there is potential competition between them. It was concluded that Dezhou should be regarded as the priority control region of the river basin. All three typical cities showed better adaptabilities to the change of forest coverage rate, water consumption per 10⁴ CNY GDP and water exploitation and utilization indices. All three typical cities had the largest number of niche overlap on the indicator of water resources per capita, indicating that the similar utilization of water resources may cause competition among the selected cities. In addition, water resources per capita, GDP per capita, water production modulus and environmental use of water in the city can be regarded as control indicators, among which water resources per capita should be regarded as the priority control indicator.