Abstract: In order to find a suitable method for measuring the water content of multiple geomaterials, an interaction model between electromagnetic wave and mixed media was built based upon polarization mechanism. The relationships between dielectric constant and each of material, porosity, and water content of multiple geomaterials including silt, sand, clay, paper, plastic, organics, and municipal solid waste were studied by time-domain reflectometry (TDR) technique. The results show that the dielectric constant of different geomaterials is mainly determined by its water content and porosity, and slightly influenced by its material type. The theoretical model proposed is suitable for geomaterials with different material type and porosity. In addition, the square root of dielectric constant is in good linear relationship with volumetric water content. The dielectric constant of geomaterial has a negative correlation with its porosity under the same volumetric water content. Furthermore, the water content of organics can be measured by TDR technique nondestructively, which provides an experimental basis for the use of TDR in landfills.