Abstract: Calcareous sand is widely spread in the South China Sea. As a special type of soil, its physical and mechanic properties vary from place to place, that always bring troubles to engineers to determine the parameters for design. With the rapid development of ocean engineering, this problem has caught great attention in practice. In this paper, the physical and mechanic properties of calcareous sand from the South China Sea and Arabian Bay are studied by indoor tests. The results show that under the same particle gradation, the dry unit weight of the sands in Arabian Bay is higher than that in South China Sea, if they have same relative density. The relationship of stress-strain exhibits soften for Arabian Bay sand and stiffen for the South China Sea sand. When relative density Dr=0.30, the friction angle of calcareous sand in the South China Sea and Arabian Bay is about 33°. However, with the increment in Dr, the friction of South China sand increases faster than that of Arabian Bay sand. When Dr=0.80, the friction angle of calcareous sand in the South China Sea is up to 37.9°which is greater than 34.9° of Arabian Bay sand obviously. The results of scanning electron microscope (SEM) reveal that the inner pore of calcareous sand in the South China Sea is more developed, and the particles have higher angularity. These characteristics should be taken into account when building platform on calcareous sands in practice.