Single-atom catalyst(SAC)has become a new frontier in heterogeneous catalysis in the past several years.[1-3] Recently,experimental findings have shown remarkable selectivity on hydrogenation reaction over graphene-supported SACs.[4] Inasmuch as chemoselective hydrogenation is one of the most effective methods to remove acetylene impurity from ethylene,in this work we have performed periodic DFT calculations to investigate the reaction mechanism of acetylene hydrogenation catalyzed by single/double vacancy graphene(SV/DV-G)supported single-atom Pt1 catalyst.