Research has not yet fully addressed the impacts of historical and future urbanization on the ecological environment in arid and semiarid regions. Using multitemporal MODIS and land use data from 2010 to 2020, in this study, the ecological effects of land use/cover change in the Lanxi urban agglomeration were evaluated on the basis of a remote sensing-based ecological index (RSEI) and landscape metrics. The patch-generating land use simulation (PLUS) model was used to identify the drivers of land use/cover transitions and simulate the land use pattern for 2030. A stepwise regression model was used to estimate future RSEI trends, and Geodetector was used to identify the dominant factors that shape spatial differentiation. The results revealed a mutual land use/cover transformation, with grassland (361.70 km2) and unused land (178.58 km2) showing the greatest reduction. The RSEI value has tended to increase (0.006/a) over the past decade. How-ever, landscape fragmentation due to urban land expansion is evident and unavoidable. Considering only land use/cover changes, the negative impact on the regional RSEI in the future is limited. This is because the RSEI for urban land (0.45) is slightly lower than that for grassland (0.50) and farmland (0.54). Precipitation (0.39) and vegetation cover (0.85) are important drivers of spatial variation in the RSEI. Precipitation and distance to truck roads are important drivers of urban development, whereas water resources and road accessibility are the basis for urban development. Therefore, considering the unique characteristics of the region, this research offers scientific and theoretical guidance for future urban expansion.