Abstract: Calcareous sand is a special geotechnical medium developing in ocean which composes more than 50% CaCO3.Compared with silica-sand,it has unexpected engineering mechanical properties due to origin and special fabic.So many researchers were attracted to research into it.This paper summarized the situation and progresses of calcareous sand in home and abroad,and elucidated in detail the resrarches on the concept and distribution region,its mechanical properties,and foundation types in it.Taking constructing runway on one island of Nansha for example,the paper discussed the feasibility of large engineering on coral reef.Furthermore,the author pointed out that researches on the microcosmic mechanism of particle breakage and its influences on mechanical properties of calcareous sand should be strengthened and the corresponding mechanical models should be built.The foundation types in calcareous sand and how to extract the design parameters should pay much more attention.Engineering environment,the structure and mechanical property of rock and soil masses,the stability of coral reef and so on should be made further studies for build large project on Islands.