Abstract: Against the background of the energy transition, the importance of geothermal resources has become increasingly prominent. The northern part of the Jizhong Depression, where the Xiong'an New Area is located, hosts the most abundant hydrothermal geothermal resources in eastern China. The carbonate reservoirs in this region feature moderate burial depth, relatively high temperature, large water yield, and favorable reinjection conditions. However, the hydrothermal circulation processes in these reservoirs remain poorly understood, the renewal rate and sustainable utilization capacity of the fluids are still unresolved. Taking the Taihang Mountains−Xiong'an New Area as the study area, based on structural geology and isotope hydrogeology, systematically analyzed the δD, δ¹⁸O and ¹⁴C isotopic characteristics of fluids in different zones and strata. Recharge sources were identified, fluid circulation pathways were clarified, fluid residence times in different subregions were calculated, and the fluid renewal capacity was quantitatively evaluated. The results indicate that geothermal reservoir fluids within the uplifted areas of the depression (where Xiong'an is centered) are recharged by paleo-meteoric water originating from the western the Taihang Mountains. The recharge elevation ranges from 317 m to 717 m, with a recharge temperature of 5.07−8.94 °C. The ¹⁴C ages of geothermal fluids were corrected and calculated via the Tamers and other models, revealing that the fluid residence time exceeds 14 000 years, with a sharp increase in groundwater age after the fluids enter the depression. Integrated with tectonic settings, temperature logging data, and field test results, the fluid circulation pattern was determined: meteoric water infiltrates through bedrock outcrops in the Taihang Mountain, converges into piedmont faults and stratigraphic interiors, migrates eastward along faults via multiple pathways to the deep depression, and finally ascends through fault zones to the Jixian System strata in the Xiong'an New Area. The regional fluid renewal rate is calculated to be 0.002 6%～0.148 8% per year, which is significantly controlled by fault distribution and tectonic conditions. The recharge rates of different circulation pathways were quantified, and the groundwater runoff velocity along flow paths ranges from 1.1 m/a to 23.5 m/a. Spatially, the runoff velocity is the highest in uplifted mountainous areas, moderate near faults within the new area, and the lowest in local uplifts and sags.