The invention discloses a processing method of a protein powder product from small trash fishes, and the processing method comprises the operation steps: 1) pretreatment; 2) degreasing; 3) enzymolysis; 4) deodorization; 5) ultrafiltration; 6) desalting; and 7) spray drying. The processing method of the protein powder product from small trash fishes has the beneficial effects: the processing method takes the small trash fishes as the raw material, has low cost, increases a treatment route for the low-value small trash fishes, carries out reasonable application of resources and increases the added value of the small trash fishes; the prepared protein powder from the small trash fishes has small molecular weight, is easy to digest and absorb by a human body, and has no fishy smell, high purity and activity of protein, and excellent product quality; during enzymolysis, infrared temperature control is adopted, thereby greatly shortening the production cycle and reducing the time cost and manpower cost; and the processing method is simple, high in reproductivity and suitable for large-scale production.