Abstract: The extracellular polymeric substances(EPS), a class of sticky material with high concentration of carbon, is consists of acidic polysaccharides.EPS is mainly produced by phytoplankton in marine environment.EPS is grouped generally into three categories:EPS cell coating, soluble EPS, and transparent exopolymer particles (TEP).EPS can dissolve in the water column, belonging to the dissolved organic carbon pool.However, EPS can form TEP of particles, belonging to the particulate organic carbon pool, via coagulate or bubbling.EPS can be absorbed or degraded by microorganisms and thus directly involve in carbon cycle within microbial loop.TEP can form marine snow by aggregating bio-organic particles, accelerating the sinking of organic carbon.Therefore, EPS is the bridge of dissolved organic carbon and particulate organic carbon, and plays key roles in shaping of the structure and function of in the marine ecosystems.This paper overviewed the current research progress of EPS, including, characteristics, formation mechanism, impact on the accumulation of cells and the contribution to the marine carbon cycle.