The evolution of submarine channels and their sedimentary units under a million-year scale is related to factors such as sediment supply, sea-level change, paleotopography and tectonic movements. However, the changing rate of sea level has not been deeply associated with the type, scale, and sand-body distribution of submarine channels and their surrounding sedimentary units. Taking the central Oligocene submarine channel in the northern Atlantic basin as an example, based on three-dimensional seismic data cube, seismic-facies characteristics of submarine channels with their sedimentary units were characterized. 90°-phasing transformation and stratal slicing techniques were used to depict the planar distribution of submarine channel with sedimentary units. Frequency spectral decomposition was used to analyze the evolution of sedimentary units and the distribution of sand bodies. The sedimentary model of submarine channels with changing rate of sea level at a million-year scale was established. The results indicate that from the early to late Oligocene, a composite system of sandy submarine channel-terminal fan, a composite system of sandy-muddy filled submarine channel-crevasse fan and a composite system of muddy submarine channel are developed in sequence. The mass transport deposits are always accompanied. Sedimentary evolution process is mainly controlled by global sea level and can be divided into a slow sea-level dropping period of early Oligocene, a rapid sea-level rise period of middle Oligocene and a rapid sea-level dropping period of late Oligocene. The slow sea-level fall is conducive to the transportation of coarse terrestrial clastics through submarine channels into the oceanic basin, which is an important prerequisite for the formation of sandy submarine channels, terminal fans and large associated mass transport deposits. Therefore, sand bodies are most developed in the lower Oligocene.