Abstract: The estuary is a key channel linking land and sea. Each year, a large amount of dissolved inorganic carbon is input into the marginal continental shelf seas through the estuary. It leads to the change of carbon source and sink pattern. In this paper, the distribution characteristics of the key carbon cycle parameters of 28 rivers around Bohai Sea in summer are plotted, and the direct input fluxes of dissolved inorganic carbon of the main rivers entering the Bohai Sea in summer are estimated. The direct input fluxes of dissolved inorganic carbon of Laizhou Bay, Liaodong Bay and Bohai Bay are 0.66 TgC、0.44 TgC、0.17 TgC. Yellow river contributes majority dissolved inorganic carbon fluxes into Laizhou Bay, which accounts for more than 50% of the total dissolved inorganic carbon fluxes into the Bohai Sea. Furthermore, Daliao river and Shuangtaizi river contribute 20% of the dissolved inorganic carbon fluxes.