The single atom solution is proposed for the CO₂ methanation. The catalytic mechanism of single atom solution on the methanation of CO₂ is studied. The catalytic performance of single atom solution with different solution proportions was experimentally determined. It was found that each gram of metal atom afforded to produce 294.50 g of methane and 9.24 g of hydrogen. The stability of catalytic performance and good cycling performance of the CO₂ conversion reaction were verified. A DFT model was developed to analyze the microscopic mechanism of CO₂ methanation by single atom solution. It was found that the reaction path formed by COOH* intermediates is the more easily realized reaction path. It is calculated that the conversion of CO* to HCO* was the rate-limiting step of the optimal reaction path, which corresponded to a limiting potential of 0.85 V. The conversion of CO₂ by single atom solution provides a new direction.