[Objective] Temporal and spatial pattern changes and driving factors of a water conservation function in the Beijing-Tianjin-Hebei region were analyzed in order to provide scientific support for ecological protection and construction in the process of regional coordinated development. [Methods] Using the InVEST model and a water conservation formula with basic geographic data and relevant parameters for the study area, the temporal and spatial pattern change characteristics and main driving factors of a water conservation function in the Beijing-Tianjin-Hebei region from 2000 to 2019 were analyzed. Spatial analysis methods such as univariate linear regression, coefficient of variation, and land use transfer matrix on the ArcGIS platform were also used. [Results] ① The average annual water yield in the Beijing-Tianjin-Hebei area was 1.87×10¹⁰ m³. The spatial pattern of water yield was high in the east and low in the west. ② The spatial pattern of water conservation in the Beijing-Tianjin-Hebei region was higher in the Yanshan and Taihang Mountains (varying from northeast to southwest), and lower in the Bashang Plateau and the Hebei Plain (varying from northwest to southeast). ③ The amount of water conservation varied greatly from year to year, and the annual average amount of water conservation was 7.85×10⁹ m³ (lowest in 2002 and highest in 2012). On the pixel scale, the area of the enhanced area of water conservation function was larger than that of the weakened area from 2000 to 2019. The enhanced area accounting for 67.49% of the study area. The weakened area accounted for 32.51% of the study area. In the past 20 years, the water conservation function could be characterized as being “mainly medium and low fluctuations, with strong fluctuations in a few areas”. The low fluctuation and relatively low fluctuation areas accounted for 93.96% of the total area, and the medium fluctuation, relatively high fluctuation, and high fluctuation areas accounted for 6.04% of the total area. ④ The main driving factors for the change of the water conservation function in the Beijing-Tianjin-Hebei region were precipitation, potential evapotranspiration, and land use changes. The depth of water conservation in typical areas had a significant positive correlation with precipitation, and a significant negative correlation with potential evapotranspiration. With regard to land use changes, ecological projects such as returning farmland to forest and grassland increased the area of forest land and grassland, and relatively increased water conservation capacity. Expansion of industrial and mining construction land encroached on the area of forest, grass, and cultivated land, and water conservation capacity has been relatively reduced. [Conclusion] The temporal and spatial patterns of the water conservation function have noticeable changed in the Beijing-Tianjin-Hebei region. The main driving factors of the water conservation function are meteorological factors and land use changes.