Referring to the definition and classification method of oasis proposed by previous researchers, the artificial and natural oases were extracted in the downstream of the Tarim River. After that, this paper analyzed the area change characteristics, transformation process, gravity center migration, and spatial variation of oasisization and desertification during the period of 1990-2015. The results show that, from 1990 to 2015, the total area of oasis in the downstream of Tarim River Basin decreased firstly and then increased. The area of artificial oasis continued to expand with a 10-year average growth rate of 46. 78 km². The area of natural oasis continued to shrink, but increased after 2000. It is because that the amount of river discharge decreased, resulting in the degradation of grassland and the reduction of natural oasis before the ecological water transport(1990-2000). After the ecological water transport(2000-2015), some unused land was utilized again. The center of the oasis traveled to the northwest, then to the south, and finally to the southeast. In addition, the oasis mainly expanded to the northwest and southeast, while the oasis reduction area was sporadic.