The invention relates to a method for preparing a NO2 adsorption reducing material, which belongs to a method for preparing a gas purifying material and solves the problems of higher micropore proportion, lower mesopore proportion and low NO2 selective adsorption of active carbon prepared by the traditional preparation method. The method sequentially comprises the steps of carbonization, activation and modification processing. The invention can obtain active carbon with high specific surface area, the specific surface areas of a mesopore and a micropore are obviously improved, and the specific surface area of the mesopore is improved to more than 40 percent; and the prepared adsorption reducing material can be used for purifying an inspiratory nitric oxide gas treating relevant diseases, such as acute lung injury and persistent pulmonary hypertension of the new born, high altitude pulmonary edema, lung transplantation reperfusion injury, acute respiratory failure, pulmonary hypertension, and the like, and also be used for separating a NO and NO2 mixed gas to produce a NO gas with high purity.