Based on the Landsat TM/ETM remote sensing images of the middle reaches of Tarim -river basin, using RS/GIS technologies, the land use/cover type information in 1990, 2000 and 2010 was extracted in this paper, the changing rule and the area ratio of the artificial and the natural oases was analyzed, and the suitable area ratio of the artificial and natural oasis was discussed. The results showed that: From 1990 to 2010, artificial oasis expanded continuously, natural oasis area in the middle reaches of Tarim River basin shrank, artificial oasis area increased 2296.69 km2, and natural oasis area decreased 2221.5 km2, the expansion speed was 114.83 km2/a and the decreasing speed was 111.08 km2/a. From 1990 to 2010, there was a trend of natural oasis replaced by artificial oasis, grassland and forest land transformed to arable land, The vegetation growing declined: high covered grass transferred to middle and low covered grassland, middle covered grass changed to low covered grassland, shrub land gradually degraded to grassland, and low covered grassland changed to desert. The artificial and natural oasis area ratio increased in recent 20 years, in 1990, 2000, 1990, artificial and natural oasis area ratiowere 1∶39.7，1∶17.4 and 1∶9.8 respectively. When there was increase of 1 artificial oasis area 1.7 natural oasis area would lose.