The middle and western part of the South China Sea is the transitional zone between the northern and southern parts of the South China Sea. It is located between the Indo-China block and the seafloor spreading center of the South China Sea, and its special geomorphology has important significance for the study of the geomorphology and geological features of the South China Sea. Based on the data of water depth, sediment survey and seismic profile obtained by the Guangzhou Marine Geological Survey Bureau as well as the results of previous studies, the authors extracted the information of geomorphology and compiled the geomorphologic map of the central and western parts of the South China Sea. The study area was divided into three secondary landform units, i.e., continental shelf, continental slope and deep sea basin, and many subordinate landform units such as submarine bank, submarine beach, marine ridge, canyon, pockmark, terrace, basin, marine platform, marine mountain, marine fan, and marine plain. This paper describes the characteristics of the landform units in this area, and puts forward geological factors such as faults, volcanoes, tectonic uplift and turbidity, which are the main factors of geomorphologic formation in this area.