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^-1and 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^-1in 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 km² and it accounts for about 21.19% of the total area;the reduced account for 17.52% of the total area about 8 173 km².The results showed that the ecological health of Qilian Mountains is improving in the overall,although it deteriorated in the local.