The Cation-interaction is increasingly recognized as an important non-covalent molecular interaction relevant to the fields of chemistry and biology. In this work, we determine the interaction energy of the system by computing the energy of the free graphene sheets and Cations and compared with the energy of graphene sheets interact with cationic polypeptides in various distances. The Lenard-Jones function and parameters have been calculated and have been fitted for exhibited an empirical function via molecular dynamics methods.