Abstract: On basis of the twophase seepage theory in unsaturated soil, a computational model, which can be used to calculate the twophase flows of compressible air and incompressible water in porous media, is proposed using the Galerkin finite element technique. A new threedimensional program is developed. The program is verified by applying it to an example of insitu air sparging and soil vapor extraction facility to remedy sites contaminated by volatile hydrocarbons.