To improve the value of surimi products, the feasibility of adding soluble protein recovered from surimi rinse water to surimi was explored. The amino acid composition, heavy-metal content, and volatile-flavor compounds in the soluble proteins recovered by flocculation from surimi wash-water were determined, and the nutritional value, safety, and flavor characteristics of the recovered proteins were evaluated. Furthermore, the optimum amount of the recovered protein to be added was determined using whiteness and gel strength of surimi as quality indicators. The results showed that the total amino acid content, the value of essential amino acids (EAA)/total amino acids (TAA), and essential amino acid index (EAAI) were 73.11%, 43.95%, and 70.04%, respectively, showing a high nutritional value. The levels of heavy metals (lead, cadmium, mercury, chromium, and arsenic) were lower than the allowable values of the national standard, showing a good food safety profile. The samples were further analyzed by gas chromatography-mass spectrometry (GC-MS) and sensory analysis. The protein recovered from surimi wash-water had an obvious fish-like flavor without an unpleasant odor. The gel properties of hairtail surimi were improved by adding the recovered protein, and the optimum amount of supplementation was 3%. This study indicates that the soluble protein recovered from surimi wash-water is safe and high in nutritional value, and addition of the recovered protein can enhance surimi whiteness and improve its gel properties.