The invention discloses a production process of brominated SBS, and belongs to the technical field of flame retardant production, and the production process comprises the following steps: adding SBS and isobutanol into a reaction kettle, heating to 20-40 DEG C, stirring, and keeping the temperature until the materials are completely dissolved; adding sodium bromide, introducing oxidizing agent chlorine, filling lime milk at the tail end of the reaction kettle to absorb unreacted chlorine in the reaction kettle, and heating to 60-75 DEG C and then stopping heating; cooling to 20 DEG C, adding acatalyst, and continuously heating to 75 DEG C to react for 1 hour, wherein the catalyst being tin tetrachloride and ferric trichloride; and cooling to room temperature, adding peroxide and alkali metal alkoxide into the material liquid after the reaction is finished, heating to 30-40 DEG C, keeping the temperature for 2 hours, filtering, washing, removing impurities, and drying to obtain the target product brominated SBS, wherein the peroxide is hydrogen peroxide, and the alkali metal alkoxide is sodium methoxide. The preparation of the brominated SBS is realized by adopting a direct bromination method, the reaction is mild, the bromine content, the yield and the thermal stability of the brominated SBS are improved, and the use requirements are met.