Highly crystalline and pure lithium metasilicate (Li2SiO3) and lithium disilicate (Li2Si2O5) nanomaterials were synthesized by hydrothermal method and characterized by PXRD technique. The changes in the morphology and particle size of the synthesized nanomaterials with reaction time were investigated using SEM technique. The UV-Vis and photoluminescence spectra of the compounds were studied. The intensity of the bands in the emission spectra increased with increasing reaction time in both compounds. The electronic band structure along with density of states (DOS) calculated by the DFT method that indicated Li2SiO3 and Li2Si2O5 had an indirect energy band gap of 4.575 eV and 4.776 eV, respectively. The optical properties, including the dielectric, absorption, reflectivity and energy-loss spectra of the compounds were calculated by DFT method and analyzed based on the electronic structures.