The invention relates to a catalyst for preparing aromatic polycarboxylic acid through liquid-phase oxidation. The invention mainly aims to overcome the problem of high usage amount of bromine in conventional catalysts used for preparation of aromatic polycarboxylic acid through liquid-phase oxidation of polyalkyl substituted aromatic hydrocarbons. The catalyst comprises a Co salt, a Mn salt, a Ce salt, a bromine-containing compound and anthraquinone monosulfonate, wherein a weight ratio of Co to Mn to Ce to Br to anthraquinone monosulfonate is 500: (200-300): (20-100): (1000-2000): (5-20). With such a technical scheme, the above technical problem is overcome, and the catalyst can be used for production of aromatic polycarboxylic acid through liquid-phase oxidation of polyalkyl substituted aromatic hydrocarbons.