This study focused on developing single-atom silver-manganese catalysts for converting the increasingly concerning CO2 to highly demanded methane (CH4) with renewable solar energy via artificial photosynthesis. The performances of the Ag supported manganese oxides (Ag/HMO) and the single-atom silver-manganese catalysts (Ag-HMO) were tested and compared under the same conditions. The activity of Ag-HMO reached as high as 0.61 mol mol(-1) catalysts, which was 1.53 times higher than that of Ag/HMO. The single-atom Ag chains in Ag-HMO promoted the electron transfer from Ag to HMO, the adsorption of visible light and the activation of adsorbed CO2, thus enhancing the photocatalytic performances. This research will be beneficial for the practical application of solar energy with plasmonic photocatalyst.