The invention provides a method for purifying acarbose from an acarbose-containing solution and aims at solving the problem of effectively controlling and reducing the content of impurities A in the acarbose production process. The neutralization of an acidic acarbose eluate is performed on a weakly alkali ion exchange column and the operation is simple and convenient; meanwhile, the abnormal increase of the component A of the acarbose due to partially excessive alkali in the process of neutralization by use of an alkaline solution or by use of a static state is avoided. The method comprises the following specific operation process: treating the acarbose-containing solution by use of a weakly acidic solution to obtain the filtrate containing the acarbose, putting the filtrate through a weak-acid ion exchange column, neutralizing by use of a weakly alkaline resin, next, separating and purifying by use of a strong acidic resin, and then concentrating by use of a nanofiltration membrane and performing spray drying, thereby finally obtaining the finished acarbose product having the component A content of lower than 0.6%. The method is simple in separation process; besides, the component A content of the crude product of the acarbose is effectively controlled, the process of independently separating the component A is avoided and the total yield is greatly increased; in short, the method is suitable for industrialized production.