Abstract: There are many evolution and attenuation mechanisms of stress waves in media, which are mainly controlled by the constitutive factors of the material and the structures geometric factors. Scientific utilization of these mechanisms have important academic and engineering values. In this paper the 2-D numerical simulation code RENEWTO are used to study the attenuation mechanism and the evolution law of stress waves in the concrete material with a cavity. By the method of changing the location and the dimension of the cavity, the attenuation of the intensity and the evolution of the shape of the stress wave behind the cavity are discussed, and the insulation effect of the cavity are analysed too. The results show that the cavity weakens the wave intensity behind it greatly. An approximation formula is presented. This work provides an important basis for designing the scientific intelligent safe protected-layer.