Although single-layered graphene has high thermal and electrical conductivity and elastic modulus, its hydrogen adsorption ability is not promising to be used in solid state hydrogen storage systems. In this study, we doped metal atoms on single graphene sheet to improve the hydrogen storage ability. Al, Li, Ni, Mg, Ti metal atoms are considered and three structural positions (Bridge, Hole, Top) on graphene are tested to derive Fermi Energy. Both Generalized Gradient Approximation as parametrized by Perdew, Burke, and Ernzerfhof(GGA-PBE) and Localized Density Approximation(LDA) are used in DFT simulations for the exchange correlation functional to calculate the doping energy between graphene and metal atoms. Finally, hydrogen adsorption ability at each positions of doped graphene and pristine graphene are compared by hydrogen adsorption energy.