Many Ground-penetrating radar (GPR) profiles acquired on the dry aeolian environment have shown a strong reflectivity inside the present-day dunes. Changes in water content are believed to be the origin of this reflectivity. In this paper we try to model the radar reflections coming from the bottom of a dry aeolian dune by using the 1D wavelet modeling method. The principle of this method is to calculate the effects of the propagation (absorption, dispersion and geometrical spreading) and reflection on a reference wavelet for different values of various parameters, and the best fit between the observed and calculated data leads to the optimum set of parameters. By combining the wavelet modeling method with a semi-empirical mixing formula for the bulk permittivity of moist sandy soils we estimate the water content and explain the importance of this latter parameter on reflection coefficient and on wavelet modeling. ¿ 2001 American Geophysical Union