Embedding a single atom into the supported catalysts is the most effective way to maximize the catalytic efficiency, holding promise for developing low-cost electrocatalysts. Grain boundaries in graphene display unique structures and have attracted great research efforts in electronic properties, catalysis and sensors. By using density function theory (DFT) calculations, we systematically investigated the potential of a single transition metal (TM) atom (TM = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ag, Au, Pt) supported on the experimentally realised 558 grain boundary (GB), as a highly efficient electrocatalyst for hydrogen evolution reaction (HER). We find that the Fe, Co, Ni and V atom anchored on 558 GB can substantially tune the free energy of hydrogen adsorption to a more optimal value, especially for the V atom ( = −0.01 eV), which is very close to, or even better than the most active Pt and MoS2 catalysts. This feature is attributed to the charge transfer between TM atom and the adsorbed H atom, which significantly promotes the proton adsorption and the reduction of kinetics. In addition, a large number of electronic states near the Fermi level ensure efficient electron transfer. Our study may provide a new cost-effective, highly active and earth-abundant HER electrocatalyst for hydrogen production.