Abstract: The water depth of the northwestrn South China Sea varies from tens of meters at the near shore area up to 3 500 m in the deep sea basin. Geomorphologically, the study area includes shelf, slope,oceanic basin and reefs, and the sedimentary environments are quite complicated. Detailed analysis of the seismic and sedimentary faices of the Late Quaternary in the study area have been carried out base on thousands of kilometers of high resolution single-channel seismic profiles.There are a total of 11 types of seismic facies distributed including the delta, paleo-river, erosional channel by turbidity current, offshore deposit, shallow sea deposit, hemipelagic deposit, pelagic deposit, slide body, deep slope deposit and carbonate platform. Further research shows that the distribution of different sedimentary facies is controlled by the bathymetry, geomorphology, and tectonic movement in the study area.