This study is on the mathematical modeling and its verification of the retardation phenomenon of gas migration in an unsaturated zone of very little moisture content The adsorption of VOCs onto the surface of the dry medium was taken into account, which has not been usually considered in the conventional models. The trichloroethylene(TCE) gas migration predicted from the mathematical model developed in this study fits the experimental results obtained from a dry glass-bead column and a dry silica sand column very well The model developed in this study gave much better prediction than did a coventional model.