The land desertification characteristics in the kern oasis area of the lower Heihe River basin were analyzed using remote sensing image data with support of GIS technique. The studied results showed that desert area steadily increased in recent 20 years, reaching about 31 km²; saline-alkali land area was 465.97 km² in 2001, increased by 82.29 km² compared to 1990; and since the water transfer project was implemented in 2002, the saline-alkali land area started to decrease, but increased again in 2010. In recent 20 years, sandy land area steadily increased, but forest land and grassland area continuously decreased and their inter-conversion was frequent. Among different land cover types, the forest land, grassland, saline-alkali land, sandy land and water bodies varied greatly. Socioeconomic and population factors have a significant influence on the land desertification in the study region. Under the background condition of natural factors, the effects of human factors on the spatial-temporal distribution of water resources decide the evolution direction of the oasis in the study region.