The invention relates to a catalyst capable of lowering the bromine index of mixed aromatics, a preparation method of the catalyst and application of the catalyst in the bromine index lowering of the mixed aromatics. The preparation method includes: mixing, by mass, 5-50 parts of aluminum oxide, 10-15 parts of zirconia, 10-30 parts of titanium dioxide and 10-30 parts of silicon dioxide, dropwise adding dilute nitric acid to assist catalyst forming, and drying after the forming to obtain a catalyst precursor; preparing 0.1-10 parts of modifier into a modifier solution; impregnating the catalyst precursor in the modifier solution, filtering, and calcining to obtain the catalyst. The preparation method has the advantages that compound metal oxides are used as the carriers, surface functionalization of the catalyst is performed by using the modifier, and the solid catalyst which can effectively remove olefin in the aromatics and efficiently lower the bromine index.