In this paper, we examined key processes for evaluating biological carbon sink in relation to marine phytoplankton in the China Sea. Current phytoplankton carbon-sink-related processes are discussed, including primary production, phytoplankton sinking, zooplankton fecal pellet package effects, the marine food chain, phytoplankton dissolved organic carbon production and subsequent bacterial repackaging, transparent exopolymer particles (TEP), and changes in phytoplankton functional groups under projected rising pCO₂. Marine primary production and the TEP aggregation web are specifically examined. Key regional study areas in China, such as the central Yellow Sea and the Yangtze River estuary, are also discussed, as well as suggestions for future biological carbon sink studies in China using diatoms, a keystone functional group.