Under global warming, desertification has brought threats to the ecological environment of arid and semi-arid regions like the Loess Plateau. It is helpful to understand the spatial-temporal trend of desertification for ecological environment projects and desertification management in these regions. The vegetation cover and its spatial distribution can reflect the degree of desertification effectively. It is an efficient way using the remote sensing techniques to observe the trend of vegetation cover and subsequently the development of desertification. The data of GIMMS AVHRR NDVI from 1986 to 2006 on the Loess Plateau were used, and the vegetation cover index was then calculated based on the principle of the dimidiate pixel model. The correlation between degree of desertification and vegetation cover was determined based on researches of wind and water erosion in the study area. The results showed that about 64% of the plateau presented moderate and severe degrees of desertification with 10%-50% vegetation cover. A third of total plateau belonged to the slight and non-desertification degrees with vegetation cover greater than 50%, and only 3% areas were subjected to extreme desertification with vegetation cover less than 10%. From 1986 to 2006, desertification generally showed a decreasing trend on the Loess Plateau. The areas with moderate and severe degrees of desertification decreased significantly, while the areas without desertification had an apparent increase. However, the area with extreme degree of desertification expanded. The degree of desertification showed a changing rule with a decadal interval. The moderately and severely desertified areas shifted reciprocally and frequently. The areas transferred between slight and non-desertification degrees were sparsely scattered. The extremely desertified areas appeared mainly along the Yellow River of Ningxia and Gansu provinces.