Marine carbon cycle is the mostly important part of the global carbon cycle，which is the key to controlling the changes of the global climate. The oceans are a huge reservoir of carbon and have the capacity for absorbing and retaining CO2, which plays an important role in regulating the levels of atmospheric CO₂. The study of carbon transfer and carbon end-result in the ocean would help us to forecast the concentrations of atmospheric CO₂ in the future, and also the changes of global climate. This paper presents the main advances in research on the marine carbon cycle and biogeochemical processes, which include the air-sea CO₂ exchange process, the carbon vertical and horizontal transfer in seawater, the carbon flux between seawater and sediment, the input flux of the river and the marine carbon cycle model etc. The total inorganic carbon (TIC) is the main carbon species in seawater, whose concentration is about 1.5～2.5 mmol/kg. The air-sea CO₂ flux is about 1.6～2.0GtC/a calculated from formula and model. There is still some controversy over the exact figure and its future changes, especially if it involves considerable uncertainty such as the function of air-sea CO₂ transfer coefficient which incorporates with many physical factors. The uptake capacity for CO₂ varies significantly due to many factors: solubility of CO₂, seawater partial pressure, carbonate system of mixed layer, temperature, salinity and alkalinity. All of these are various in different seawater, which would act as carbon source or sink of atmospheric CO₂, along with the influence of seasonal and inter-annual variability. The vertical transfer of carbon in seawater is mostly various and complex processes, but mainly depends on the biological pump. The atmospheric CO2 is translated into dissolved organic carbon (DOC) and particulate organic carbon (POC) by photosynthesis of phytoplankton and biology metabolism, which is pumped into the deep seawater by food chain processes, physical mixing, transport and gravitational settling. The primary production of global marine ranges from 36.5GtC/a to 103GtC/a, but the majority of which is recycled within the euphotic zone supplying a standing stock of marine microorganisms. It is also estimated that for primary production about 4GtC/a to 20GtC/a is exported to the deep ocean. The major part of export production pumped into the deeper seawater column is also remineralized during sinking; only 0.03% to 0.8% of primary production can be delivered to the sediment. The concentrations of DOC and POC usually are very abundant in surface and subsurface of most oceans, and decrease with the depth of seawater, however, they will keep a lower constant value in deep seawater. The contents of DOC in seawater range from 60μmol/L C to 90μmol/L C in the surface, about 40μmol/L C in the deep. The distributions of DOC and POC show a decreasing trend from the inner shelf to the slope and to open sea because of the river inputs and higher primary productivity. The carbon benthic flux of seawater-sediment interface is one of the important aspects of marine carbon cycle. The remineralization of POC in the sediment and the diffusion of DOC across the sediment-water interface can increase the concentrations of DOC and DIC; enrich the dissolved nutrients in deep seawater. The nutrient-enriched deep seawater also is taken to the surface by the adverse/diffusive upwelling and recycles in the euphotic zone by biological activities. Carbon derived from land also enters into the ocean via river as well as to some extent via groundwater; the global natural transport flux from river to the ocean is about 0.8GtC/a. The marine carbon cycle model has been built up to stimulate all kinds of physical, chemical and biological processes in the ocean. The model forecasts the atmosphere conditions in the pre-industrial and the climate changes in the future, and also estimates the controlling functions of increasing CO₂ concentrations into the ocean. The model includes a lot of styles such as BM, GCM and B-GCM etc, and develops from one dimension to three dimensions. The three dimensional biological geochemistry model would be the important and efficient tool for studying the marine carbon cycle. The latest development of determining DOC and POC, and the future for the direction of marine carbon cycle is also summarized in the paper.