Abstract: Large-river dominated ocean margins (RiOMars) are, as a major repository of terrestrial materials and one of the most important active sites for burial and remineralization of organic matter on the Earth's surface, play an important role in global biogeochemical cycles of carbon. The research advances in biogeochemistry of sedimentary organic carbon (SOC) in RiOMars were reviewed in this paper concernings of transport, burial and remineralization of organic carbon. The nature of SOC, e.g. sources, composition, size and density fractions can significantly influence its distribution and fate in margin systems. The special sedimentation environment in RiOMars, for example the mobile muds, plays a unique role in organic carbon transport, burial and remineralization. Microbial metabolism enhances the decay of SOC, especially the refractory terrestrial organic materials in the margins. Comprehensive studies based on integrated techniques of molecular biology, organic geochemistry and biogeochemistry are helpful to reveal the role of special microbial and phytoplankton functional types in biogeochemical cycles of SOC in RiOMars, and to understand the biogeochemical cycles of biogenic elements in estuaries and continental margins.