The proluvial plains in Northwest China, formed by seasonal flood debris along the piedmont, are critically important for regional ecological security. Characterized by expansive deserts, scarce precipitation, and limited surface runoff, these proluvial plains are highly susceptible to global climate change and rapid urbanization. Systematically revealing the spatiotemporal patterns of landscape ecological risk (LER) driven by land use/cover change (LUCC) is therefore essential for managing these fragile proluvial ecosystems. However, existing studies specifically focused on proluvial plains remain limited, and the region's unique geomorphology has created a fragmented land cover matrix, introducing biases into traditional LER assessment schemes. To shed some light on this topic, this study develops an optimized framework through the integration of a landscape ecological risk index (LERI) with the patch-generating land use simulation (PLUS) model to investigate the spatiotemporal dynamics of LER from 1985 to 2050. The results yielded the following findings: (1) From 1985 to 2020, bare soil and grassland areas decreased by 20,334.0 km2 and 5,779.3 km2, respectively, while cropland expanded by 22,186.7 km2. Concurrently, the overall LER decreased during this period, with high-risk regions shrinking by 23,183.9 km2. (2) In multi-scenario simulations, cropland is projected to increase by 3,444.3 km2 under the cropland protection (CLP) scenario, whereas under the ecological protection (EP) scenario, grassland will increase by 1,133.3 km2 as bare soil decreases by 2,219.2 km2. (3) The CLP scenario is projected to yield the lowest overall LER, achieving a 9.1% net risk reduction area. Conversely, the EP scenario results in the highest LER, with only a 1.19% net risk reduction, highlighting a trade-off between localized ecological restoration and landscapelevel fragmentation. These findings provide significant scientific guidance for refining territorial planning strategies and achieving the harmonious coexistence of ecological conservation and economic growth in arid and semi-arid regions.