With the discovery of graphene in 2004, a new line of research in two-dimensional materials was unveiled. As this innovation we find the transition metal dichalcogenides (TMD) materials that became known as last generation graphene since these systems have many degrees of freedom to be explored and understood. We can find the TMD in three different phases, which depends on the number of electrons in the d orbital of the transition metals and the size of the atoms. Usually these materials are found in three polymorphs schematized in 1T, 2H and 3R, where the number represents the number of layers of the unit cell and the characters indicate the trigonal, hexagonal and rhombohedral symmetry, however according to some crystalline systems of these new materials of the TMDC type that we only find in the cubic phase. In this work, we use first principle calculations, based on the Density Functional Theory (DFT), using the generalized gradient (GGA) and local density (LDA) approximations and the PBE and CAPZ functional, used in optimizations and property descriptions structural, electronic and optical, implemented in the computer code CASTEP, to investigate the optical electronic properties of transition metal dichhalcogenides (TMD). The present work consists of the study of materials with the following formation $ RuX_2 $ com (X = S, Se é Te). As a result, it was seen that the polymorphic systems of the type $ RuX_2 $ their phase is extremely cubic, through the theoretical models of the theory of bands we noticed that the polymorphs have semiconductor characteristics of indirect gap. With the results of the optical properties we calculated $ \ epsilon_ {0} $ for all structures of the type $ RuX_2 $ using the functional GGA-PBE and LDA-CAPZ