Abstract: Based on the MODIS data and Landsat data during the period from 2000 to 2014, the temperature vegetation drought index was used to reflect the surface humidity, and the temporal and spatial changes of surface humidity and vegetation cover on the Loess Plateau since implementing the Grain for Green Project were analyzed. The findings suggested as follows: ① The growth rate of normalized vegetation index in the Loess Plateau during the period from 2001 to 2014 was 6.3%·(10a)^-1, the temperature vegetation drought index was decreased by -4.5%·(10a)^-1, the vegetation cover and surface humidity were increased, the vegetation coverage was high in the southeast but low in the northwest, and it could be generally seen that there was a positive correlation between the surface humidity and the vegetation coverage; ② According to the change trend of TVDI and NDVI, the vegetation cover and surface humidity were in an increase trend in the Loess Plateau. The spatial change of vegetation cover was in accordance with the variation of surface humidity perfectly, but there was a regional difference; ③ The correlative coefficient indicated that there was a positive correlation between the vegetation cover and the surface humidity in the Loess Plateau. From the perspective of the change trend, the changes of vegetation cover and surface humidity in the northeast-southwest zone of the Loess Plateau in 14 years were beneficial to the improvement of ecological environment. Intensive human activities in the plain are very unfavorable to the improvement of ecological environment. It is worth to pay attention to the key areas where the Grain for Green Project is implemented because they are critical for monitoring and managing the ecological environment change in the future so as to avoid degenerating again.

Key words: vegetation cover, surface humidity, spatiotemporal evolution, Grain for Green Project, Loess Plateau