Abstract: Objective: To study the effect of bifidobacterium on irritable bowel syndrome(IBS).Methods: Eight-four patients with IBS were administered 3-4 pieces of bifidobacterium each time for three times per day and the symptoms were assessed every week before and after bifidobacterium therapy.Results: The total response rates of two and four weeks after the therapy 63.38% and 83.40%,respectively.The effect was more obvious on mitigating of abdominal pain,abdominal distension,abdominal tone and diarrhea.Conclusions: Bifidobacterium is effective for treatment of IBS syndrome with little side effect.