This paper investigates the oasis expansion and land use changes in arid Manas River Valley using imageries of Landsat MSS, TM and ETM, land use and topographic maps. Over last 50 years, oasis area increased from 156.385km2 in 1949 to 5042.440 km2 in 2001. Oasis expansion process over last 50 years can be divided into oasization and urbanization stages according to the rate of increase. Farmland quickly increased from 156.4 km2 in 1949 to 3639.5 km2 in 1976 during the oasization stage with an annual increase rate of 129.004 km2/a. In urbanization stage from 1976 to 2001, urban area increased from 22.481 km2 to 75.257 km2 with an annual increase rate of 2.111 km2/a. The driving-force analysis reveals that human activities of reclamation and population growth played a major role in oasis expansion in Manas River Valley. With the oasis expansion, a series of eco-environment problems such as sand invasion, pasture degeneration, soil saltization and land abandonment have become more and more seriously. The issues of how to improve the efficiency of water resource usage, protect mountain and desert environments, deal with saltization problems in oasis have become the most important research topics of oasis expansion and sustainable development over these oasis.