Understanding how climate change and human activities impact ecosystem services (ESs) is crucial for optimizing urban planning, land resource allocation, and ecological protection. This study simulated various land use scenarios in northwestern China using a coupled system dynamics model (SD) and a patch-generation land use simulation model (PLUS) under Shared Socioeconomic Pathways and Representative Concentration Pathways (SSP-RCP) scenarios. The In-VEST model was used to assess ecosystem service levels and trade-offs for 2030. We analyzed these using correlation coefficients and Geographically Weighted Regression (GWR) models. The results indicate: (1) The SSP126 scenario, which promotes ecological restoration, leads to a shift from cropland to grassland. The SSP245 scenario continues current development trends, optimizing unused land. The SSP585 scenario emphasizes economic growth, resulting in significant cropland expansion. (2) Ecosystem service levels for WY, CS, and SC are higher in the northwest and southeast but lower in the central region, with HQ showing the opposite pattern. The Comprehensive Ecosystem Service Index (CESI) under SSP126 is notably higher, making it preferable for long-term ecological development in the northwest. (3) Except for WY-HQ, most ecosystem services exhibit synergies, though trade-offs and synergies vary spatially. WY-HQ trade-offs are concentrated in the southeast, while SC-HQ synergies are strongest in the northwest. This research aims to mitigate the effects of human activities and climate change on ecosystem services, enhancing ecological security and sustainability in northwestern China and Central Asia's arid zone.