Abstract: A dynamic global vegetation model based on the annual land-use change data was used to quantify water conservation capacity with respect to grassland changes in the Yellow River above Lanzhou between 1980 and 2020 using different scenario simulations.The results showed that the average annual water conservation in this region was approximately 24.21 billion cubic meters, with grassland ecosystems contributing approximately 20.28 billion cubic meters, accounting for 83.8% of the total water conservation.Before 2002, the water conservation capacity exhibited a decline trend (-0.51 billion cubic meters per year).However, an increasing trend was observed after 2002 (0.35 billion cubic meters per year).Changes in the grassland in the Yellow River above Lanzhou, while having negligible negative impacts and no discernible regional differences, resulted in an annual reduction of 0.67 billion cubic meters in the regional water conservation volume between 2015 and 2020.Simulations were performed under scenarios representing different degrees of grassland degradation.The results showed that mild degradation caused changes in the components of grassland evapotranspiration, which in turn led to a slight increase in the regional water conservation volume; however, this effect decreased significantly as the degree of degradation increased.