The invention provides a catalyst for flue gas demercuration. The catalyst is prepared from titanium dioxide as a carrier, the carrier is doped with manganous bromide, and the mass ratio of the manganous bromide to the titanium dioxide is 4-15 to 100. The invention further provides a preparation method for the catalyst for flue gas demercuration. The preparation method comprises the following steps: dissolving soluble manganous bromide into deionized water, and stirring at a normal temperature; after the manganous bromide is completely dissolved, putting titanium dioxide into the manganous bromide solution, wherein the mass ratio of the manganous bromide to the titanium dioxide is 4-15 to 100; carrying out ultrasonic water bath treatment on the mixed liquid; after ultrasonic water bath treatment, leaving the mixed liquid to stand at the room temperature; putting the mixed liquid after standing into a baking oven, and drying, so as to obtain the catalyst for flue gas demercuration. Thecatalyst provided by the invention has demercuration efficiency of 100% even at 200 DEG C or greater, is simple and rapid in preparation method, is capable of remarkably improving flue gas demercuration efficiency under a condition without HCl, and has certain poisoning resistance.