Abstract: The thermal conductivity of calcareous sand in the South China Sea is measured under different conditions by the thermal probe method, and the effects of water content, dry density, temperature, particle size and other factors on the thermal conductivity of calcareous sand are discussed. The results show that the thermal conductivity of calcareous sand increases with the increase of the water content and dry density, and the higher the water content, the more significant the influences of dry density on thermal conductivity. The thermal conductivity of calcareous sand increases with the increase of the temperature, but the thermal conductivity of calcareous sand varies with the increasing trend of water content at different temperatures. The particle size has little effect on the thermal conductivity of calcareous sand. Adding a certain amount of quartz sand into the calcareous sand helps to improve its thermal conductivity.