The East China Sea (ECS) has been reported to be a significant sink of atmospheric CO2, but less is known about horizontal transport of dissolved inorganic carbon (DIC) across the shelf. A coupled physical-biogeochemical model has been implemented for the ECS to simulate the inorganic carbon system and estimate CO2 fluxes and cross-shelf DIC transport in the ECS. A 6-year model hindcast (2013–2018) was performed and assessed. Multiple existing datasets from in-situ observations are used to constrain and validate the model. The model reproduces the spatial and temporal patterns of nitrogen, chlorophyll and CO2 parameters in general agreement with observations. Modeling estimation reveals that the ECS takes up CO2 at an annual mean rate of about 8.20 ± 3.13 mmol m−2 d−1, and experiences substantial seasonal variability. The total annual CO2 uptake in the ECS is about 21.55 Tg C yr−1. Modeling estimation suggests that the biological processes contribute to about 15 % of the shelf CO2 uptake in the ECS, leaving ~80 % of the shelf uptake contributed by other physical-chemical processes, e.g., physical pump and/or solubility pump. The horizontal fluxes of DIC between the ECS and the adjacent ocean are more than two orders of magnitude larger than the air-sea CO2 flux on the ECS and result in a net DIC export of about ~33.8 ± 14.87 Tg C yr−1 from the shelf area. Modeling results suggest that this conveyance of DIC to the open ocean is equivalent to about 70 % of the inorganic carbon inflow from riverine and atmospheric pathways in the annual scale.