The invention discloses a liver-protecting oral liquid and a preparation method thereof, and belongs to the technical field of healthcare food processing. The preparation method comprises the following steps: adding water into degreased wheat germ powder to uniformly stir, and adding neutral protease to perform enzymolysis to obtain wheat protein hydrolysate, adding maltose and food-stage sodium selenite into the wheat protein hydrolysate, sterilizing, cooling and performing bread yeast fermentation to obtain bread yeast fermentation liquor; sterilizing the bread yeast fermentation liquor to obtain a yeast nutrient solution; uniformly mixing the yeast nutrient solution with grape juice to obtain mixed juice; adding monopotassium phosphate and magnesium sulphate into the mixed juice, sterilizing, cooling and inoculating a grifola frondosa strain to ferment to obtain grifola frondosa fermentation liquor, and grinding the grifola frondosa fermentation liquor through a mycelium colloid mill to obtain nutrient serous fluid, and filtering, mixing, pouring, sealing and sterilizing the nutrient serous fluid to obtain a finished product. The oral liquid disclosed by the invention is safe todrink, is good in mouthfeel, is thick in fruity smell, and further has the effect of protecting liver.