The invention discloses a method for preparing ginger beer, which comprises the steps of pasting, saccharifying, wort filtration, boiling, sedimentation, cooling, fermentation, filtration and filling. In the saccharifying step, when the temperature rises to 44 DEG C, fresh ginger juice of which the amount is 0.4 to 0.6 volume percent of that of setting cold wort is added; the steps of saccharifying, wort filtration, boiling, sedimentation, cooling and fermentation are carried out continuously; after the fermentation is completed, fresh ginger juice of which the amount is 0.4 to 0.6 volume percent of the total amount of fermentation liquor is added; and the mixed solution is uniformly mixed and filtered and filled to obtain the ginger beer. In the method, part of ginger juice is added first in the saccharifying step to enable amylase in a saccharified boiler to decompose a small amount of starch in the ginger juice to prevent the starch from influencing the stability of colloid, but part of the ginger juice component can be lost by the steps of wort filtration, boiling, sedimentation, cooling, fermentation and the like; and therefore, another part of the ginger juice is added afterthe fermentation is completed to supplement the nutrient and aroma of the ginger juice lost by the previous steps.