[Objective] To explore the spatial and temporal changes and causes of water and soil conservation services in the Sanjiangyuan region.[Methods] Based on NPP quantification, soil and water conservation services from 2000-2020, and driver analysis with parameter optimal geographic detector.[Results] The results show that: (1) from 2000 to 2020, the land use in Sanjiangyuan area, cultivated land, grassland, water area and construction land area are expanding, and forest land and unused land area decrease; the Sanjiangyuan area is mainly grassland, followed by water area and woodland, while cultivated land and construction land area is relatively small. In 20 years, the vegetation coverage basically showed a trend of steady increase, with a whole spatial distribution pattern of "high in the east and low in the west".(2) From 2000 to 2020, the soil conservation service capacity index in Sanjiangyuan shows the "N" type trend, but generally increasing trend, the growth rate is 26.13%, and the soil conservation service capacity is significantly improved; the distribution of soil conservation service capacity is consistent, showing the spatial distribution pattern of "high in east and low in west". From 2000 to 2020, the center of gravity of the Sanjiangyuan area is always in the west of Maqin County. The soil and water conservation capacity increases to the northwest direction and extends in multiple directions, and the project implementation effect is remarkable.(3) Vegetation coverage, GDP per land, and grazing intensity have a great impact on water and soil conservation services. The explanatory power of many factors, such as vegetation coverage, ground average GDP, annual average rainfall and grazing intensity, is strong.[Conclusion] We should continue to implement natural forest protection projects, carry out forest conservation and restoration to greatly increase the forest stock; take reasonable grazing, artificial grassland construction, fencing and replanting measures to protect the ecology.The research results can provide scientific basis and data support for the ecological environment protection and sustainable development in Sanjiangyuan.