Rapid socio-economic development in Xinjiang has substantially increased the level of urbanization (UL) in the Aksu region, exerting significant impacts on the ecological environment. As a key component of the strategic ecological security pattern in the Xinjiang Uygur Autonomous Region, the Aksu region plays essential ecological roles, including wind prevention, sand fixation, and improvement of living conditions. In this study, UL was assessed from four dimensions: social, spatial, economic, and population. Ecological environmental quality (EEQ) was evaluated using the Remote Sensing Ecological Index (RSEI) on the Google Earth Engine (GEE) platform. The Coupling Coordination Degree (CCD) model was then applied to explore the spatiotemporal interactions between UL and EEQ from 2005 to 2021. The results show that: (1) UL displayed significant spatial heterogeneity, with higher levels in the east and lower levels in the west, as well as a moderate shift in its spatial center of gravity. Overall, UL exhibited a significant upward trend. (2) At the county level, EEQ generally improved, with higher quality in the north and lower quality in the south, showing marked hierarchical differences among counties. Regionally, RSEI values increased over time, though the ecological condition remained relatively poor. (3) The CCD between UL and EEQ rose steadily, indicating enhanced coordination, yet regional disparities persisted, with a continued polarization in coordinated development. These findings provide empirical evidence to support sustainable urban development and ecological governance in arid and semi-arid regions.