Deformation modulus of subsoil is an indispensable parameter for calculating settlement of foundation based on elastic theory; whereas the deformation modulus of subsoil is usually not provided in geotechnical investigation reports in China. Previous published researches are analyzed in this paper. An approximate method that considers the influencing factors including Poisson ratio
porosity ratio and remolding of soil
is developed based on porous medium theory. It estimates the deformation modulus of subsoil through compression modulus. It has practical significance in both calculating settlement of foundation with elastic theory and making full use of the existing research data.