Abstract: In order to investigate the vibration isolation performance of a wave impeding block (WIB) in unsaturated soil foundation and to improve the frequency width of vibration isolation of conventional homogeneous WIBs, the vibration isolation effect of double-layer WIBs in unsaturated soil foundation under an underground dynamic load is studied upon the theory of single-phase elastic and unsaturated porous medium. Using the Fourier transform and Helmholtz vector decomposition, one calculation formula of the dynamic response of unsaturated soil foundation under underground dynamic loading is established. Analyzed for the influence of physical and mechanical parameters are elastic modulus, density, thickness, embedded depth, load frequency and soil saturation on the vibration isolation performance of the double-layer WIB. The results show that the best vibration isolation effect of double-layer WIBs can be obtained by designing the elastic modulus and density of each layer of WIBs. At the same thickness, the vibration isolation effect of the double-layer WIB is better than that of the homogeneous WIB. The double-layer WIB enhances the frequency width of homogeneous WIB vibration damping, which has a better vibration isolation effect on low, medium and high-frequency vibration (5 Hz≤f≤80 Hz). When the thickness of double-layer WIB exceeds the critical thickness, the vibration isolation effect decreases with the increase of thickness. Soil saturation has a significant effect on the vibration isolation effect of the double-layer WIB, and the double-layer WIB can achieve a better vibration isolation effect at a low saturation.