Abstract: To enhance the understanding of runoff responses to climate and vegetation changes, co-variation diagnosis based on Copula functions, structural equation modeling, and elasticity coefficients were employed in the less human-impacted northern foothills of the Qinling Mountains, to analyze the runoff response patterns under the collaborative changes of climate and vegetation. The results showed: ① From 1980 to 2022, the basin exhibited a trend of nonsignificant increase in precipitation, significant increase in leaf area index. ② Improvement in vegetation conditions led to a decrease in the proportion of precipitation converted into runoff. ③ Temperatures is the primary climatic factor driving regional vegetation changes, which in turn affected runoff. ④ Vegetation changes adapting to climate change amplified the runoff response to temperature changes while reducing the runoff response to precipitation changes; a 1°C increase in temperature directly caused a 2.7% reduction in regional runoff and indirectly led to a 3.8% reduction by driving vegetation changes; a 10% increase in precipitation directly increased regional runoff by 17.2%, but indirectly reduced runoff by 1.5% through driving vegetation changes. This study holds significant scientific importance for understanding the hydrological response patterns of watersheds under the co-variation of climate and vegetation.