Abstract: The nutritional value of walnut protein was evaluated based on the amino acid composition, and the effects of walnut protein and walnut protease hydrolysate on disease activity index score, serum inflammatory factors, myeloperoxidase activity and colon tissue morphology were investigated in mice with acute colitis induced by sodium glucan sulfate (DSS). The results showed that walnut protein had a reasonable amino acid composition. The essential amino acid content (26.98%), the predictive value of protein efficacy ratio (PER, 1.55 and 1.58) and the biological value (BV, 87.96%) were high. After digestion in mice, walnut protein and its hydrolysate could retard the onset of colitis, slow down the weight loss of mice caused by colitis, and significantly improve the clinical symptoms. Serum biochemical indexes showed that both walnut protein and its hydrolysate could extremely significantly (P<0.01) reduce the contents of IL-1β, IL-6, TNF-α and myeloperoxidase (MPO) activity in serum of acute colitis mice. The histopathology of colon tissue showed that both walnut protein and its hydrolysate could significantly improve the morphological characteristics of the colon in colitis mice, alleviate the damage of colon tissue, and reduce the infiltration of inflammatory cells. In conclusion, walnut protein could prevent and retard the occurrence and development of acute colitis after gastrointestinal digestion.