The invention relates to a denitration catalyst and a preparation method thereof. The preparation method of the denitration catalyst comprises the following steps: 1) Mn salt and Ce salt are dissolved in water, the solution is heated, a metal salt solution is formed, and a regulator is added to regulate pH to 4-7, wherein the mole ratio of Mn to Ce as metal elements in the metal salt solution is 1:(0.01-0.2), and the Mn salt comprises a component A and a component B; 2) a carrier is added to the metal salt solution in batches, the mixture is heated and stirred, and slurry is obtained; the weight ratio of the metal elements to the carrier in the metal salt solution is (1-30):100; 3) the slurry is dried in vacuum and smashed, and denitration catalyst powder is obtained; 4) the denitration catalyst is kneaded and roasted, and the denitration catalyst is obtained. The preparation method of the denitration catalyst adopts a simple process, and scale production can be realized; the catalyst is high in activity, and the performance of the catalysts in different batches is stable.