The present invention relates to the field of biology, in particular to a sugar preparation method by using biomass sweet potato dregs for microbial fermentation as a sugar source. The liquid sugar product prepared with the method of the present invention essentially comprises the ingredient of glucose. The method of the present invention is of simple process, high specificity, good product quality and high yield, and solves the serious environmental pollution problem of the sweet potato dregs, thus having a good industrial application prospect.
