This study focused on Zhangjiakou City, a key water conservation area in the capital region and an ecological barrier in the Beijing-Tianjin-Hebei region. By integrating the Patch-generating Land Use Simulation (PLUS) model and the Geographically Weighted Regression (GWR) model, we quantified land-use changes and the trade-offs/synergies among four ecosystem services (windbreak and sand fixation, food production, soil conservation and water conservation), under different development scenarios from 2000 to 2020 and for the 2030 projection. Based on the trade-off/synergy perspective, we identified the optimal development scenario for Zhangjiakou City. The results indicated that: 1) From 2000 to 2020, the area of forestland in Zhangjiakou City expanded by 40.63%, while cultivated land, grassland, and water bodies declined significantly, intensifying spatial conflicts among ecosystem services, with trade-offs becoming dominant. 2) Four development scenarios, including natural development, cultivated land protection, ecological protection, and comprehensive development, were simulated. The multi-scenario simulations showed that ecosystem services generally exhibited an improving trend across all scenarios. However, conflicts between food production services and ecological regulation services remained prominent. The ecological protection scenario enhanced the synergy between windbreak and sand fixation and water conservation services. The comprehensive development scenario improved the synergy between food production and various ecological regulation services. 3) The comprehensive development scenario, which balanced the coordinated economic development, cultivated land protection and ecological protection, was identified as the optimal scenario for Zhangjiakou City. Future efforts should focus on strengthening comprehensive development planning in Zhangjiakou City to achieve sustainable regional development.