Abstract: Agricultural water constitutes a significant portion of global water resource consumption, particularly in arid regions, where agricultural productivity depends heavily on scarce water supplies. The oasis irrigation district of the Yarkant River Basin, a key agricultural production region in China, faces increasing water scarcity challenges along with intensified competition for water resources. This study systematically investigated the temporal and spatial variations of planted area, irrigation arable area, accumulated irrigation area, water diversion amount, and irrigation quota from 2000 to 2021, as well as evapotranspiration (ET) and irrigation efficiency from 2000 to 2020, in the oasis irrigation district of the Yarkant River Basin. Utilizing Mann-Kendall trend analysis, Sen’s slope estimation, and Pearson correlation analysis, this research analyzed long-term trends based on irrigation data and the Penman-Monteith-Leuning Evapotranspiration Version 2 (PML-V2) ET dataset. The key findings included the following: 1) Although the water diversion amount significantly decreased, river and reservoir water remained the primary source, accounting for 81.0% of water diversion amount. The total planted area and irrigation arable area both showed highly significant increases, whereas changes in the accumulated irrigation area were not significant. The water allocation quota showed a highly significant decreasing trend, whereas the irrigation water quota showed a significant decreasing trend. Cotton and wheat remained the dominant crops, their accumulated irrigation area occupied 37.1% and 21.4% of the total accumulated irrigation area, respectively. The monthly accumulated irrigation area was notably concentrated in summer (from June to September), accounting for 55.2% of the annual accumulated irrigation area and aligned with the period of high river runoff. The correlation between water diversion and river runoff gradually weakened, indicating the need for adaptive water resource management strategies during drought periods. 2) ET displayed a significant upward trend, particularly in upstream and downstream regions, averaging 401 mm annually of the whole region. Irrigation efficiency exhibited highly significant improvement, rising from 25.1% in 2000 to 43.7% in 2020. Spatially, the ET values were higher in continuously cultivated farmlands, and lower in intermittently cultivated areas. Additionally, validation through water balance analysis confirmed that the PML-V2 ET dataset maintained adequate reliability in this arid region, providing valuable reference data for subsequent eco-hydrological studies. These insights into water resource management practices, crop irrigation patterns, and irrigation efficiency enhancement will contribute critical knowledge for sustainable agricultural development and resource management strategies in arid irrigation districts.