The invention relates to a C9+ aromatic hydrocarbon lightening catalyst, comprising a high-temperature-resistant inorganic oxide carrier and the following components accounted by taking the dry basis carrier as benchmark: 0.01-10.0 weight percent of hydrogenation metal, 0.01-1.0 weight percent of IVA-group metal and 0.1-5.0 weight percent of halogen; wherein, the hydrogenation metal is selectedfrom iron, cobalt, nickel and iridium. The catalyst is used for lightening C9+ heavy aromatic hydrocarbon. The catalyst has high lightening transformation ratio, high aromatic hydrocarbon yield andless carbon deposition; and the catalyst can effectively lower final boiling point and gum level of the heavy aromatic hydrocarbon.