The invention discloses a preparation method of a walnut polypeptide beverage. The preparation method of the walnut polypeptide beverage comprises the following steps: step one, removing red peels of walnut kernels; step two, rinsing the walnut kernels with the removal of the red peels by using water, carrying out vacuum freeze-
drying and then squeezing to obtain 
walnut oil and walnut 
meal; step three, crushing the walnut 
meal into walnut 
protein meal, and 
softening; step four, pulping to obtain walnut 
protein raw liquid, separating pulp and residues, and homogenizing to obtain walnut 
protein liquid; step five, adding 
alkaline protease into the walnut protein liquid for carrying out enzymolysis; step six, carrying out 
enzyme deactivation to obtain a walnut polypeptide solution; and step seven, adding auxiliary materials into the walnut polypeptide solution, adding water for making up to the volume and then homogenizing to obtain the walnut polypeptide beverage. The content of 
small molecule peptide with the molecular weight being less than 2000Da in the walnut polypeptide beverage prepared by adopting the method reaches over 95%; the walnut polypeptide beverage prepared by adopting the method is low in 
peptide molecular weight, very high in content of 
peptide components, good in product taste, suitable for being eaten by large groups of people, good in product stability, very good in 
oxidation resistance and 
fatigue resistance, and is capable of reducing 
blood pressure and improving the immune function and the absorption function of a 
human body.