By using the remote sensing data and the climate data of DEM elevation model calibrated in 2003-2012,we estimated the net primary productivity(NPP)of Qilian Mountains vegetation based on CASA model.The years,annual variation of NPP,the temporal-spatial distribution and change trend were also analyzed.The results reveal that:(1)The NPP in Qilian Mountains is mainly concentrated during the summer (June to August),it accounts for 86.39% of the total NPP;From 2003 to 2007,Minor fluctuations between 165.28 g· m~(-2)·a~(-1)and 192.75 g· m~(-2)·a~(-1) in the annual average of NPP;NPP showed a significant downward trend from 2007 to 2009,by 168.63 g· m~(-2)·a~(-1) down to 153.17 g· m~(-2)·a~(-1);while,NPP showed a clear upward trend from 2009 to 2012,the maximum value can reach 207.13 g· m~(-2)·a~(-1).(2)The spatial distribution of NPP in Qilian Mountains showed a rising tendency from west to east.NPP in most of the eastern regions varied from 200 to 400 g· m~(-2)·a~(-1),in some areas up to 500 g· m~(-2)·a~(-1).There were obviously differences between the north and the south in the central region;NPP in most of the southern regions varied from 100 to 300 g·m~(-2)·a~(-1),but it varied from 100 to 400 g· m~(-2)·a~(-1)in most northern regions.NPP in most of the western regions was between 0 and 100 g· m~(-2)·a~(-1),especially the desert and alpine ice snow covered area had the lowest biomass.(3)NPP in the Qilian Mountains has been increased volatility in the recent ten years;the area of NPP increased about 9 867 km~2 and it accounts for about 21.19% of the total area;the reduced account for 17.52% of the total area about 8 173 km~2.The results showed that the ecological health of Qilian Mountains is improving in the overall,although it deteriorated in the local.