[Objective] The spatiotemporal variation characteristics of water ecosystem services in the Haihe River basin were analyzed, and the impact patterns of climate, land use change, and water ecological governance measures on water ecosystem services were explored, in order to provide a scientific basis for the healthy management of water resources in the river basin. [Methods] Water yield and water purification were selected as the core water ecosystem services in the Haihe River basin. Using the InVEST model, the water yield and water purification functions were simulated for nine periods from 1985 to 2023 in the river basin. Scenario analysis was applied to calculate the contribution rates of climate and land use to changes in water ecosystem services, and the GTWR model was used to quantify the impacts of climate, land use, and water ecological governance factors on water ecosystem services. [Results] ① From 1985 to 2023, water yield exhibited an overall fluctuating upward trend, with a multi-year average of 105 mm. Spatially, water yield increased in the central and southwestern regions and decreased in other regions.② From 1985 to 2023, the total nitrogen(TN) export, representing the water purification function, showed a fluctuating upward trend, while the total phosphorus(TP) export declined continuously and then stabilized. Spatially, N and P exports increased in the southern region and decreased in the northern region.③ The contribution rates of climate and land use to changes in water yield were 56% and 44%, respectively. Increases in inter-basin water transfer volume, precipitation, and water area enhanced water yield, while increases in temperature and evaporation inhibited it. The contribution rate of climate to changes in both N and P exports was 61%, and that of land use was 39%. Increases in wastewater treatment and reuse volume, evaporation, and water area promoted the water purification function, while increases in temperature and precipitation inhibited it. [Conclusion] The spatiotemporal heterogeneity of water ecosystem services in the Haihe River basin is jointly driven by climate, land use, and water ecological governance measures. High-intensity human development activities have increased water resource utilization intensity and simultaneously caused degradation of the water purification function, while water ecological governance measures have effectively alleviated this trend.