n the case of a rapid wetting and drying, water movements result in a rapid change in capillary pressure. The models used until now to predict the shrinkage process of most porous media are based on the quasistatic behavior laws and totally neglect the dynamic effects. The main purpose of this paper is to put forward a widespread model based on the poromechanics theory to coupling the deformation of porous matrix and the unsaturation two phases flow (water-air) under the condition that considering the dynamic capillary effects and phase transformation. Thereafter this widespread model is simplified based on Richards' equation which means that air pressure is constant and equals to atmospheric pressure. And this new model is written into finite element software COMSOL Multiphysics to simulate the water-air two-phase flow inside of soil. The simulation result proves that dynamic effects have a non-negligible influence on the fluid-solid coupling. And its influence is obvious when suffering a sudden and rapid change of surrounding relative humidity. The closer to the surface or interface, the dynamic effects is greater.