Abstract: Piezoelectric sensors have been widely applied in geotechnical engineering,especially in characterizing soils through measurement of wave velocities.Since mechanical properties of a material are closely associated with wave velocities,piezoelectric sensors provid a reliable and non-destructive method for the determination of soil properties.The following results of recent researches were presented on measuring stiffness of a wide range of soils such as clay,sand and gravel,characterizing anisotropic properties of soil induced by external loading,measuring stiffness of base and subgrade materials in the pavement,determining soil properties in a centrifuge model during the flight of a centrifuge,and understanding wave propagation in granular materials under micro-gravity environment with this technique.It was shown that piezoelectric sensors could be widely and effectively used in researches and practices of geotechnical engineering.