In the electrochemical Bunsen reaction, which is the key reaction of the sulfur-iodide cycle, the main overpotential corresponds to the oxidation of SO2. The catalysts currently used for the liquid phase electrocatalytic oxidation of SO2 are mainly based on noble metals, which have excellent corrosion resistance and catalytic activity in an acidic environment. To improve the performance of the commercial Pt catalyst, a Pt catalyst with reduced graphene oxide (RGO) and carbon black as a hybrid support was synthesized by the microwave-assisted polyol reduction process. The large two-dimensional planar structure of RGO was a better anchor for Pt nanoparticles, and a catalyst with fine and uniform distribution of Pt particles was obtained. The carbon black interior prevented the agglomeration of RGO, forming a stereoscopic catalyst structure. The electrochemical test results showed that the RGO/carbon black hybrid support catalyst possessed a higher electrocatalytic activity than the single support catalysts and could be used as an efficient and stable catalyst for the SO2 electrolyzer.