The present invention discloses a walnut protein peptide, a preparation method and an application thereof. The walnut protein peptide is prepared according to the following steps: adopting aromatic fruit plant composite protease to carry out an enzymolysis reaction on walnut separation protein to obtain the walnut protein peptide, wherein the relative molecular mass of the walnut protein peptide is mainly between 0-1000 Da, and the walnut protein peptide comprises 2-9 amino acids, has characteristics of unique flavor, high peptide content, small molecular weight, short peptide chain, no requirement of debittering, strong activity and strong diversity, and can be used as a pharmaceutical raw material and a food additive for preparation of products with effects of blood pressure lowering, anti-oxidation, memory enhancement, and brain nerve sensitivity improvement, wherein the products comprise drugs, health care products, food and the like. The preparation method for preparing the walnut protein peptide has characteristics of simple process, less investment, quick effect, high return rate, no environmental pollution, low carbon and high efficiency, and is suitable for industrial production.