In this article, the electronic band structure and charge density distribution of planar and buckled silicene are calculated by using density functional theory. The results show that the band structures of planar and buckled structures are similar except that some of the bands split in the buckled structure. Similar to the band structure, the charge density distribution of the system does not change significantly as a result of buckling except the lowering of charge density distribution symmetry in buckled structure. In both structures, the conduction and valence bands cross the Fermi level at the k point. The optical properties of silicene sheet are also investigated. The results indicate that silicene sheet shows optical anisotropy along the parallel and perpendicular polarizations. For parallel polarization, two major peak can be observed at 1.6 and 3.9 eV. The peak intensities for perpendicular polarization is smaller than that of parallel polarization and there is no significant absorption peak below 5 eV
