Abstract: Uses a reflected wave method and an oven dry method to estimate soil water content. Experimental study is carried out. The reflected wave method is based on the ground penetration radar technique. The empirical equation of experimental silt is obtained via curve fitting of soil water content versus dielectric constant. Comparative analysis shows that the classical Topp formula has a good serviceability in certain water content rang. An empirical formula is proposed in this paper. It has a wider range of estimating soil water content and a higher estimate accuracy than the classical Topp formula. This study indicates that the empirical formula is necessary for different types of soils and will help to improve the accuracy of estimation of soil water content with ground penetrating radar technique.