Due to high carbon fixation potential forced by high primary production, the continental shelf systems are significant contributors to the ocean carbon cycle that has the buffer capacity via taking up the increasing anthropogenic CO_2. However, the dynamic patterns of CO_2 sinks and sources are still obscure and the control mechanisms are known little due to the dramatic spatial-temporal variation in continental shelf. Carbon cycle in the marginal seas excluded in climate-carbon cycle coupled models will be a main uncertainty for forecasting climate change in IPCC-AR4. By using suitable continental shelf carbon cycle models, the long term variations of sinks/sources patterns, the possible contributions of key processes in carbon cycle, the interactions between carbon systems and ecological systems, and the role of continental shelf carbon cycle under climate change are estimated. The key processes considered in the models related to physical field, biological pump and carbonate system are summarized based on the researches of carbon cycle models for the continental systems, and key scientific problems to be solved, along with a basic idea to model the carbon cycle in the East China Sea, are proposed.