Through evaluating a few existing multi-source products of gross primary productivity (GPP) and evapotranspiration (ET)

we constructed combined datasets of GPP and ET for the Qinling Mountains in China. Then

the spatial-temporal variations of water use efficiency (WUE) were calculated and analyzed for the Qinling Mountains. The results indicated that the estimation effects of different products of GPP and ET were very different for different vegetation types. Generally

the

products of VPM GPP

RF GPP performed well for GPP estimation

while the products of China ET and PML-V2 ET performed well for ET estimation in China. In the Qinling Mountains

the average annual ecosystem GPP

year

was about 1 489.95 g C/m

2

; the average ET

year

was about 588.49 mm; the average WUE

year

was about 2.56 g C/kg H

2

O; and the change rate of average WUE

year

was about 0.156 g C/(kg H

2

O·10 years). The values of average WUE

year

showed a non-significant rising trend (p

>

0.05). The differences of annual average WUE

year

were not great among different vegetation types. However

the trends of WUE

year

changes were various for different vegetation types. Some vegetation types showed increasing trends

while others showed decreasing trends. The dynamics of average montly WUE

month

had two obvious peaks per year. This study provided a reference for data acquirement and selection for the research of carbon-water relationships in different ecosystems. It also deepened our understanding of the temporal and spatial changes of ecosystem WUE in the Qinling Mountains in China.