The invention discloses a preparation method for agaricus bisporus enzymatic hydrolysis peptide oral liquid. The preparation method comprises the following steps of: selecting a fresh agaricus bisporus raw material for pulping to obtain agaricus bisporus slurry; placing the agaricus bisporus slurry in an enzymatic reactor; accurately weighing acid protease and papain and adding the acid protease and the papain into the enzymatic reactor; heating to the temperature of 50 to 60 DEG C; adjusting a pH value to be maintained between 4.5 and 5.5; performing enzymolysis for 5 to 6 hours with stirring; inactivating the protease when the proteases are digested to the predetermined hydrolysis degree of 65 percent; and centrifuging, concentrating, then preparing, clarifying, filling and sterilizing to obtain a finished product. The content of the peptide obtained by the preparation method is high; the prepared oral liquid has a golden color, a good taste and no fishy smell; the product has the advantages that: the safety is high, the nutritive value is high, the process is simple, the preparation method is easy to operate, the equipment investment is less, and the production cost is low; therefore, the preparation method is suitable for industrialized production.