Using a three-dimensional coupled physical-biogeochemical model, this study examines the dynamics of dissolved inorganic carbon (DIC) in the South China Sea (SCS). The model well simulates observed DIC distributions and identifies characteristically DIC enhancement from the Western Philippine Seas (WPS) to the northern SCS by up to 140 μmol kg^-1 in the upper layer. Such an increasing pattern in DIC continues from northern SCS to southern SCS but with a much less degree (< 40 μmol kg^-1). Overall, both the spatial and temporal variations of DIC in the SCS are significantly modulated by both the intrinsic dynamics and extrinsic exchanges via various straits including Luzon Strait (LS), a major gateway linking SCS and WPS. The influx of DIC to the SCS through LS occurring in the upper layer (h < 700 m) is 12×10⁶ mol s-1 associated with the Kuroshio intrusions and is 1.8×10⁶ mol s^-1 at the deep layer (h > 1800 m) along with the SCS overflow from the deep WPS. The export fluxes of DIC are 6.8×10⁶ mol s^-1 through Mindoro and Balabac Straits and 2.9×10⁶ mol s^-1 through the SCS intermediate water outflow (700 m < h < 1800 m) via LS. The net extrinsic intake of DIC is primarily balanced by the shelf-ward transport across the 100 m isobath, accounting for 4.8×10⁶ mol s^-1. Terms balance of DIC suggests that while physical transport plays a predominated role in modulation of the DIC dynamics in the SCS, the biogeochemical process is also crucial, particularly in the upper ocean. We will also examine the fluxes ratio between DIC and nutrients and their implications on the air-sea CO2 fluxes.