Abstract: In the construction of islands and reefs in the South China Sea, the high-temperature environment problem of calcareous sand foundation requires a comprehensive understanding of the evolution laws of calcareous sand thermal conductivity. Based on the thermal probe method, the thermal conductivity of cement-cemented calcareous sand under different test conditions is determined, and the variation laws of the influence factors such as water-cement ratio, curing period, cementing degree (cement content) and moisture content on the thermal conductivity are discussed. It is found that the thermal conductivity of the cement-cemented calcareous sand increases sharply firstly and then decreases slowly with the increasing curing period. At the same time, the thermal conductivity increases with the increase of the cement content and moisture content, and decreases with the increase of the water cement ratio. On this basis, the trend of thermal conductivity of the cement-cemented calcareous sand with the degree of cementation is explained by the scanning electron microscope and mercury intrusion porosimetry tests. The result shows that the macroscopic thermal conduction characteristics of the cement-cemented sand are determined by the variation of size and quantity of its micro-pores. The gelatinous hydration products continuously fill the internal pores of cemented sand, causing a reduction in porosity and improving the internal heat transfer of the sand sample. At the macro level, the thermal conductivity increases with the degree of cementation.