Abstract: The deep water area of the Pearl River Mouth Basin, located at the northern margin of theSouth China Sea, is a key area for offshore oil and gas exploration in South China Sea, and has agood prospect for oil and gas exploration. In this paper, the characteristics of the presentgeothermal field and lithospheric thermal structure in the deep water area of the Pearl RiverMouth Basin are analyzed by means of the borehole geothermal measurements. The resultsshow that the distribution of terrestrial heat flow in the Pearl River Mouth Basin is low in the north and high in the south. Since the Eocene, the Baiyun Sag in the deep-water area ofthe Pearl River Mouth Basin has experienced two stages of extensions. The first stage（47.8～33.9 Ma）rifting occurred in the Eocene, with a large extension intensity, and the basal heatflow in the depression rose rapidly to～82 mW/m2. The second phase（23～13.8 Ma）occurred in the Miocene, which was more intense in the south of the Baiyun Sag. The main body of theBaiyun Sag reached the highest paleo-heat flow at 13.8 Ma, and then entered the thermalsubsidence stage, and the basement heat flow decreased slowly. The joint inversion of apatitefission track, apatite（U-Th）/He, and zircon（U-Th）/He show that the maximum paleo-temperature reached around 13.8 Ma, and then the temperature was basically stable.