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Based on the DFT, the adsorption and dehydrogenation reactions of methanol over PtCo@SV have been extensively investigated. When PtCo binary metal is adsorbed on the defect of single vacancy graphene (SV) by Co atom, its stability is obviously stronger than that of pure platinum on defect of SV. Both the H-adsorption and O-adsorption on Pt and Co sites are considered as initial reaction steps. Compared with Cu site, methanol is more likely to dehydrogenate at Pt site. Although the H-adsorption on the Pt site is weaker than the O-adsorption, the dehydrogenation by the H-adsorption path has much lower energy barrier than that by the O-adsorption path. Generally, for the H-adsorption path, the adsorption is rate determining step because of the rather low dehydrogenation barrier for the H-adsorption complex (thermodynamic control), whereas the O-adsorption path is determined by its dehydrogenation step (kinetic control). Among all the PtCo@SV investigated, PtCo-2 and PtCo-3 are found to enhance the activity of catalytic dehydrogenation by the H-adsorption path on the Pt site as compared with that on Pt2@SV, which explains why PtCo catalyst has become the focus of fuel cell research in recent years.