Abstract: Groundwater serves as a crucial source of replenishment for lakes in arid regions. It not only acts as an important link in maintaining the ecological health of these lakes, but also plays a vital role in the terrestrial ecosystem carbon cycle. The unique aquatic environment and hydro-ecological patterns of arid lakes make dissolved inorganic carbon (DIC) a key component in the lake carbon cycle. Dissolved CO₂ and \mathrmHCO_3^- , the main forms of DIC, are the primary sources for photosynthesis and organic matter production. Phytoplankton absorb DIC to synthesize organic carbon, part of which is oxidized and decomposed by microorganisms, while the rest settles and is buried in the sediment, making the lake a “sink” for CO₂. However, the formation of calcium carbonate precipitates from Ca²⁺ and \mathrmHCO_3^- can increase the partial pressure of CO₂ in the lake water, causing the lake to act as a “source” of CO₂. This study reviews the critical role of groundwater in the hydrological balance, carbon balance, and ecological balance of arid region lake systems. It identifies the characteristics of DIC in arid regions such as lake water. It elucidates how groundwater affects lake DIC through water cycling, hydrogeochemical interactions, and nutrient input. The applicability of monitoring technologies, carbon isotope techniques, and model simulations in studying lake DIC are also summarized and compared. Finally, future research directions for the DIC cycle in arid region lakes are proposed, focusing on the mechanisms of hydrological and biogeochemical processes influencing lake DIC, the carbon cycle characteristics of artificially replenished lakes, and the effects of lake carbon cycling and adaptive management strategies.