The utility model discloses a thin-wall denitration catalyst which comprises a catalyst body which is in an cuboid structure, a square hole array through which flue gas passes are uniformly distributed running through the catalyst body along a long-edge direction, and the hole array is by 20 holes*20 holes. The thin-wall denitration catalyst makes up the vacancy of the product specification of a thin-wall cellular catalyst in the industry to better meet various requirements of flue treatment, meanwhile, the wall thickness of the catalyst is also reduced, therefore, in a denitration process under the same condition, the thin-wall denitration catalyst has lower SO2 oxidation rate. The opening rate of the catalyst can reach 80.2%, the geometric proportion surface area can reach 482m2/m3, the contact area of flue gas and the catalyst is effectively increased, due to the larger inner diameter and higher opening rate, the ash blockage is difficult to generate in the denitration process under the same condition.