The invention relates to a method for catalyzing CO2 hydrogenation reduction by using a sulfur-containing iridium complex. A sulfur-containing substituent-substituted dipyridyl iridium complex is synthesized and used as a catalyst to catalyze CO2 hydrogenation. The method has the advantages as follows: the iridium complex has good water solubility, no organic solvent is required to be added to a catalytic reaction, and pollution caused by the organic solvent is avoided; besides, a sulfydryl dipyridyl ligand is synthesized successfully with a thiourea alkylation hydrolysis method for the first time, the preparation process is simple, and synthesis methods, such as a sodium hydrosulfide alkylation method and the like, which cause severe environmental pollution are avoided. The invention provides a novel efficient transition metal catalyst for catalyzing CO2 hydrogenation.