The Zhu III subbasin is one of three subbasins in the Pearl River Mouth Basin in the northern shelf of the South China Sea. Oil and gas exploration results, synthetic study of geochemical and thermal modeling of the two source rocks, diagenesis and organic inclusions, and basin modeling show that there are two petroleum systems in the Zhu III subbasin. These are the Wenchang-Zhujiang petroleum system and the Enping-Zhuhai petroleum system. In the two petroleum systems, hydrocarbon generation, migration and accumulation peaks are late Miocene-Holocene.