In this paper, novel filled materials EPS-blocks of cast-in-situ slabs are presented. And EPS-blocks with light weight which are inexpensive are validated to be sufficient strong as filled materials to bring an innovation for the development of cast-in-situ slabs. Based on modal analysis, it is found that the decreased weight has a greater influence to the mode of the slab than the weakened stiffness. According to harmonic response analysis, tensile stress distributions of the slab with EPS-blocks are depicted in figures and explained. Typically, orifice stress distributions are expounded and stress variations of nodes in different places are illustrated. From these studies, it is concluded that the steady state dynamic performance of the slab with EPS-blocks is good.