Calcareous sand is a kind of special medium which is composed of calcium carbonate and other diffi- cult soluble carbonate substances． Because of its rich in inner pore space and easy crashed，the mechanical property is very different from conventional quartz sand． Based on the compaction test and direct shear test of calcareous sand， by means of data fitting，the coupling relationship between compaction density and mechanical property under different water contents was obtained; meanwhile，the shear strength expression was built on the basis of the relationship between water content and dry density．