<p>The construction of a surface reservoir in a karst area will inevitably change the regional hydrogeological conditions and impact the groundwater circulation process and recharge dynamics. In this study, a representative synclinal basin-type karst groundwater system in the Yangzhuang Basin, northern China, was selected to analyze the influences of surface reservoir construction on the groundwater circulation mechanism and recharge conditions through multi-factor regime monitoring, multiple regression analysis, and the groundwater balance equation. Following the filling of the Zhuangli Reservoir, the hydraulic gradient in the karst groundwater system gradually decreased from upstream to downstream, accompanied by a decrease in the groundwater depression cone area. The flow of a downstream karst spring increased, while the responsiveness of karst groundwater levels to surface water runoff significantly decreased due to the influence of artificial storage. Karst groundwater levels remained significantly influenced by precipitation. Comparative analysis of conditions before and after the reservoir construction of the Zhuangli Reservoir showed that the amount of recharge to karst aquifers increased from 8598.56 × 10⁴m³/year to 11,731.89 × 10⁴m³/year, with seepage from the reservoir becoming one of the main sources of karst groundwater recharge in the Yangzhuang Basin. Concurrently, the discharge of karst groundwater resources decreased from 10,443.29 × 10⁴m³/year to 9994.42 × 10⁴m³/year, and the water budget for the karst groundwater system changed from negative to positive.</p>