Abstract: With the global advancement toward carbon neutrality, the development of high-efficiency, low-energy CO₂ capture technologies has become a research priority. Although molten salt-modified MgO exhibits excellent CO₂ adsorption performance under pure CO₂ conditions as a representative intermediate-temperature adsorbent, its severe performance degradation under low CO₂ concentrations significantly limits its practical application. To address this critical challenge, this study proposes a K₂CO₃-enhanced strategy and optimizes the synthesis of a 40mol% K₂CO₃-10%(Li_0.3Na_0.6K_0.1)NO₃-MgO composite adsorbent. The results demonstrate that the optimized material achieves a CO₂ uptake of 1.38 mmol/g under 20% CO₂ at 300℃, representing a 13-fold improvement over the unmodified system. Through multi-scale characterization techniques, the influence of K₂CO₃ doping on MgO and the underlying CO₂ adsorption mechanism were systematically investigated. The developed adsorbent exhibits excellent cycling stability, maintaining a capacity of 1.30 mmol/g after 20 adsorption-desorption cycles, demonstrating promising potential for industrial applications. This study not only develops a highly active intermediate-temperature CO₂ adsorbent but also provides new insights for designing efficient low-concentration CO₂ capture materials.