Transition metal catalyzed chemical vapor deposition (CVD) is considered as the most promising approach to synthesize high-quality graphene films, and low-temperature growth of defect-free graphene films is long-term challenged because of the high energy barrier for precursor dissociation and graphitization. Reducing the growth temperature can also bring advantages on wrinkle-free graphene films owing to the minimized thermal expansion coefficient mismatch. This work focuses on density functional theory (DFT) calculations of the carbon source precursor with hydroxyl group, especially CH₃OH, on low-temperature CVD growth of graphene on Cu and CuNi substrate. We calculated all the possible cleavage paths for CH₃OH on transition metal substrates. The results show that, firstly, the cleavage barriers of CH₃OH on transition metal substrates are slightly lower than those of CH₄, and once CO appears, it is difficult to break the C–O bond. Secondly, the CO promotes a better formation and retention of perfect rings in the early stage of graphene nucleation and reduces the edge growth barriers. Thirdly, these deoxidation barriers of CO are reduced after CO participates in graphene edge growth. This paper provides a strategy for the low-temperature growth of wrinkles-free graphene on transition metal substrates using CH₃OH.