The invention relates to an extraction and preparation process of walnut polypeptides. The walnut polypeptides are prepared from walnut meal and aspergillus niger, which serve as raw materials, through the steps of raw material treatment, pulping, heated sterilization, inoculation, fermentation, fermentation terminating, ultrafiltration, evaporation concentration, freeze drying, low-temperature crushing, packaging and the like. Compared with the traditional chemical methods and enzymolysis methods for producing the walnut polypeptides, the process has the characteristics of simplicity in operation, no solvent residual and low processing cost; the process has the advantages of being simple in operation and suitable for large-scale production.