[Objective] The objective of this study is to analyze the spatial and temporal changes of vegetation NPP(net primary productivity) and carbon fixation and oxygen release in the three-river headwater region during the past 14 years in order to provide scientific basis for the ecological sustainable development in this area. [Methods] NDVI

meteorological data

the land-use data and the remote sensing data were collected. The spatial and temporal variations in NPP and amounts of carbon fixation and oxygen release were analyzed based on CASA model

carbon emissions model and Sen+Mann-Kendall model. [Results] (1) The mean value of NPP was ranged from 0 to 750 g/(m2·a)

which accounted for 81.72% of the entire study area. The spatial distribution of average NPP presented a decreasing trend from southeast to northwest. And NPP in the lower altitude

rivers and dense woodland areas was higher than that in the alpine regions

which indicated that NPP was affected by altitude

rivers and land types. (2) The NPP showed an increasing trend in recent 14 years

with a growth rate of 7.26 g/(m2·a)(p>0.05). As to the inter-annual variation of NPP

about 23.64% of the study area showed a decreasing trend (2.3% of them p<0.05) while 76.36% showed an increasing trend (30.58% of them p<0.05). (3) As to the variation of carbon fixation and oxygen release

the cultivated land was larger than the forest land and other land use types. Variation of carbon fixation and oxygen release in forage land was small. [Conclusion] The alpine grassland ecosystem in the three-river headwater region was good

as it was less influenced by human beings. However

ecosystem in the low altitude

river and human activities intensive areas was complex and the locally degraded

and ecological environment in those regions need to be protected.