The invention provides a preparation method for an impurity reference substance for producing bambuterol and belongs to the technical field of pharmacy. The method comprises the following steps: introducing hydrogen into the raw material to reduce in the presence of acid and a catalyst to prepare a product, wherein the acid is selected from hydrochloric acid, phosphoric acid, acetic acid, formic acid, trifluoroacetic acid, benzenesulfonic acid, p-toluenesulfonic acid and malic acid; and the pressure of the hydrogen is lower than or equal to 180kPa.