The invention discloses a method for preparing total sugar from waste and inferior tobacco stems. The method mainly comprises extraction and purification technologies. An ultrasonic technique is introduced into the extraction process, so that the extraction speed and efficiency are accelerated; distilled water replaces an aqueous solution of ethanol to serve as an extraction solvent, so that the extraction efficiency is improved, and the extraction cost is reduced; the treatment of any acid or alkali is not involved in the extraction process, and the method is simple and environmentally friendly. In the purification industry, pigments and proteins are selectively adsorbed by an AB-8 macroporous resin, the decolorization and deproteinization processes are combined into a whole, the problems that filtration difficulty is caused by protein emulsification in the Sevage method and the like are effectively solved, the decolorization and deproteinization processes in the traditional column chromatography are avoided, and the decolorization and deproteinization efficiency of the total sugar is improved. The patent technology provides a novel pathway for comprehensive utilization of the waste and inferior tobacco stems.