<p>The carbon sink of terrestrial ecosystems serves as a crucial measure for evaluating the carbon sequestration capabilities of these ecosystems, closely tied to changes in land use. The Grain for Green Program (GGP) has led to significant shifts in regional land use, which in turn has a significant impact on terrestrial ecosystem carbon sinks. It is essential to examine the effect of the GGP on carbon sink dynamics and to elucidate the spatial and temporal variations of the carbon sink effect in Shaanxi Province. This will help enhance the GGP's outcomes and pinpoint areas for improving quality and carbon sinks. This research utilizes panel data from Shaanxi Province from 1992 to 2020. It employs the Propensity Score Matching-Difference in Differences (PSM-DID) Model to evaluate the GGP's impact on carbon sink effects and their variability. Our results indicate that the GGP exerts a significantly positive impact on carbon sinks. Without accounting for other factors, the implementation of GGP increases vegetation carbon sinks by 20.2% and elevates vegetation cover by 46.21%. After controlling for external variables, these effects further increase to 21.42% for carbon sinks and 53.51% for vegetation cover. Spatial variability analysis reveals that the most potent carbon sink effects are located in Northern Shaanxi, followed by Southern Shaanxi and Guanzhong. Temporal analysis reveals consistently positive carbon sink effects across all implementation phases, although their intensity declines progressively while maintaining statistical significance.</p>