The invention relates to a catalyst for removing oxygen and improving quality of bio-oil and a preparation method thereof. The catalyst comprises active ingredients and a carrier, and is characterized by comprising the following active ingredients and carrier in percentage by weight: 10 to 32 percent of NiO, 5 to 18 percent of MnO3, 5 to 15 percent of CoO and the balance of dolomite carrier. The catalyst has the advantages that: the cheap and readily available dolomite is taken as the carrier, and the active ingredients are compounds of nickel, cobalt and molybdenum, so that the acidity of the bio-oil is weakened and the oxygen content is reduced. The catalyst is easy to prepare, has high strength and catalytic activity, can be regenerated, can be used for preparing high-quality bio-oil from biomass, and also can be applied to preparation of hydrogen through catalytic reforming of the bio-oil.