[Objective]Gansu Province is an important water conservation and ecological security barrier area in western China, whose research on the water conservation service function is strategic for ensuring the regional ecological security and sustainable development.[Methods] Here, the dynamic changes of water conservation in the temporal and spatial scale in Gansu Province from 2001 to 2023 were quantitatively evaluated using the InVEST model, and the influencing factors of the water conservation service function were analyzed using the geographic detector.[Results] (1) The average water conservation in Gansu Province from 2001 to 2023 was 9.24 mm, and the water conservation fluctuated little in the different periods. The change of the water conservation was consistent with the precipitation and water yield, and showed an upward trend and then a downward trend. The overall distribution pattern of water conservation in the province was lower in the northwest and higher in the southeast.(2) From 2001 to 2023, the average water conservation capacity of different land use types in Gansu Province was ranked as cultivated land, grass land, forest land, urban construction land, unused land, and water area.(3)Precipitation was the most important driver for the change of water conservation in Gansu Province, and the interactions between precipitation and evapotranspiration, land use type, and elevation, respectively, had the most significant influence on the spatial difference of the water conservation service function in Gansu Province. The results showed that the change of the water conservation function in Gansu Province was mainly influenced by climate factors and human activities.[Conclusion] This study will provide scientific basis for quantitative evaluation and objective understanding of water conservation function in Gansu Province, and also provide a valuable reference for the regional water resource management decision and water conservation function restoration.