Abstract: We investigated thermal conductivity, mineral composition, grain size and geomorphy of seafloor sediments and their variations in the drilling area on the northeastern slope of South China Sea using the thermal conductivities and multi-beam data as tools. Data reveals that the thermal conductivities of seafloor sediments are 1.26±0.12 W/(m·k) higher than the background values on average, possibly due to deposition of terrigenous turbidites and methane related high-thermal-conductivity carbonate deposits. The detailed distribution pattern of the thermal conductivities is interesting. The thermal conductivities as high as 1.32±0.06 W/(m·k) and 1.34±0.06 W/(m·k) are discovered in the areas of No. 2 and No. 5 respectively on the submarine platforms where large area is deposited by coarse grained carbonate due to bottom current denudation. Thermal conductivities as low as 1.10±0.06 W/(m·k) and 1.01±0.06 W/(m·k) are found in the typical submarine troughs of No. 1 and No. 8 areas respectively attributing to the compaction of fine grained deposits avalanched from the submarine plateaus. The seafloor sediments thermal conductivity at the drilling area decreases from the central plateaus to the peripheral troughs, probably owing to the chemical composition of highly migrating fluid under the control of endogenic process and the grain size decrease up to geomorphic changes under the control of the exogenic process.