Recent findings show that the functionality of the proteins is mainly influenced by their folding states, and many of the illnesses are due to misfolding of proteins and peptides. For this reason, investigation of protein folding has recently much attention in ab-initio computational society. The goal of the present project is investigating the effects of metal ion on the folding and optical absorption spectra of the Ac-Ala4-LysH+ proteins. At first, we characterized the more important minima of the potential energy surface of the system using classical force fields and then refined these minima using quantm computations within density functional theory and the full-potential approach. Then the optical absorption spectra of the lowest energy minima were investigate using time-dependent density functional theory and utilization of the pseudo-potential technique. Then the Na + ion was adsorbed to the system and the caps of the system were removed. Similar to the pristine protein, the lowest energy minima of the potential energy surface of the ion adsorbed protein and their absorption spectras were calculated. We observed that the Na + ion replaces some of the Hydrogen bonds with stronger ion-oxygen bond and reduces the absorption spectra intensity. Moreover, these ion oxygen chemical bonds give rises to an annular form for the protein around an axis passing through the Na + ion.