Large-scale wind power development is a critical pathway for China's low-carbon energy transition. However, the cascading impacts of rapidly expanding wind farms (WFs) on regional climate and vegetation remain poorly understood. This study employs a coupled climate-vegetation model to assess the potential environmental effects of large-scale WFs in northern China and to investigate the mechanisms linking WFs with climate and vegetation dynamics. Our results show that WFs significantly alter lower atmospheric dynamics (e.g., wind speed and turbulence) at both local and regional scales, with minimal impact on temperature. Furthermore, by enhancing windward moisture convergence, vertical velocity, and regional atmospheric instability, the WFs promote summer convective precipitation in northern China's farming-pastoral ecotone (FPE). The resultant positive soil moisture anomalies, together with reduced vapor pressure deficit, collectively drive vegetation greening, leading to a widespread 1-5% increase in vegetation coverage. Sensitivity experiments further reveal that larger turbines and expanded WFs amplify these climatic-ecological effects. These findings highlight the potential benefits of wind power infrastructure for regional climate and vegetation in similar dryland regions, providing scientific insights for synergizing wind energy development with desertification control in climate-sensitive transition zones.