The Beijing-Tianjin-Hebei urban agglomeration is one of the most water-deficient regions in China and globally owing to intense human activities. Overexploitation of water resources has greatly affected the eco-environmental security, and restricted the sustainable development of the socio-economic system. Regarding the coordinated development of human-water relationships, a comprehensive evaluation index system for water resources security was constructed, which was composed of three criterion layers, i.e., natural endowment of water resources, exploitation and utilization degree of water resources, and exploitation and utilization efficiency of water resources. The thresholds and grading standards for each specific indicator and their integrated indexes were set according to the experience of developed countries and regions, so that the evaluation results could be compared spatially and temporally. Subsequently, we used an Analytic Hierarchy Process (AHP) model reformed by entropy technology to calculate their weights, and establish a multi-objective fuzzy membership function to calculate the normalized values. We used the statistical data of 13 urban regions in the Beijing-Tianjin-Hebei urban agglomeration during 2000-2014 to analyze the spatiotemporal pattern of water resources security. The results showed that: (1) for the whole region of the Beijing-Tianjin-Hebei urban agglomeration, most of the water resources security indexes were between 0.2 and 0.4, which were regarded as unsafe type during the period. However, they tended to become larger and the security type became critically safe; (2) various cities in the Beijing-Tianjin-Hebei urban agglomeration had different water resources security indexes. Generally, they were smaller in the South and larger in the North; most became larger during the period; (3) the integrated indexes of the three criterion layers also had a high degree of regional consistency and disparity. They interacted with each other spatially and temporally, and impacted the spatiotemporal pattern of water resources security in the Beijing-Tianjin-Hebei urban agglomeration.