Grasping spatial-temporal dynamics of oasis in the inland river basin is the basic premise for realizing optimal allocation and dynamic management of water resources for the inland river basin. Shule River Basin, located in the west of Hexi Corridor, is a typical sensitive area in the fragile zone of ecosystem. In recent years, with the warming of the climate, the diameter flow out of the mountains has increased year by year, providing a good environmental background for the expansion of artificial oases and the restoration of natural oasis. Many scholars had carried out a lot of research work on ecological quality, service function and carrying capacity in this basin. However, there were relatively few studies on the spatio-temporal changes of oasis pattern and structure in long time series at watershed scale. Therefore, based on Landsat data of years 1975, 1990, 1995, 2000,2005, 2010, 2015 and 2020 combining object-oriented random forest and visual interpretation method, this paper analyzed the spatio-temporal pattern, structure change and causes of oasis in Shule River Basin from 1975 to 2020. And it also discussed the impact of artificial oasis area to natural oasis area ratio on the quality of ecological environment. The results showed that:(1) The total area of oasis was 5790.24 km² in the Shule River Basin in 2020, accounting for 4.65% of the total area of the basin, of which the artificial oases, natural oases and desert-oasis ecotone accounted for 45.29%, 51.07% and 3.64%, respectively; (2) The distribution patterns of oasis in Shule River Basin are mainly the inland river desert region model and the mainstream flow model. (3) The oasis area in Shule River Basin showed an overall trend of expansion from 1975 to 2020. The oasis changes were mainly characterized by the expansion of artificial oases and the decrease of natural oasis and desert-oasis transition zones. The main changes of land cover types were the reclamation of grassland and desert. And the land cover types of artificial oasis in Shule River Basin showed an increasing trend from 1975 to 2020. The oasis changes could be divided into two stages:slow expansion from 1975 to 2000 and rapid expansion from 2000 to 2020. (4) As the ratio of artificial to natural oases area increased from 3:7 (1975) to 5:5 (2020), the eco-environmental quality of oases increased firstly and then decreased, reaching the highest value in 2005. This study can provide data support and scientific basis for the steady development of oasis ecosystem in Shule River Basin.