Objective To investigate the effect of compound Lactobacillus acidophilus on the levels of serum SP , VIP, 5-HT, IL-6 and TNF-αin patients with diarrhea-predominant irritable bowel syndrome ( IBS) .Methods 82 cases of patients with diarrhea -predominant irritable bowel syndrome ( IBS) from November 2015 to November 2016 in our hospital were selected,and randomly divided into two groups.30 patients in observation group were treated with compound Lactobacillus acidophilus tablets and 52 patients in control group were treated with trimebutine maleate capsule.The levels of serum SP, VIP, 5-HT, IL-6 and TNF-α,quality of life score,clinical curative effect and adverse reaction were observed and compared before and after treatment.Results After treatment,the diarrhea, abdominal distention, defecation frequency and abnormal rate of stool were significantly lower than those before treatment(P <0.05), the levels of SP,VIP,5-HT,IL-6 and TNF-αin serum were significantly lower than those before treatment(P <0.05),and the treatment group were lower than those of the control group.After treatment, the mental status, emotional control and work status scores of the observation group were higher than those of the control group,and the effective rate of the observation group 86.7%was significantly higher than the control group 61.5%,the differences between the two groups were statistically significant (P <0.05).There was no significant adverse events were observed during the treatment.Conclusion Compound Lactobacillus acidophilus is effective in the treatment of diarrhea-predominant irritable bowel syndrome.It can restore the levels of serum SP, VIP, 5-HT, IL-6 and TNF-αin patients with diarrhea-predominant irritable bowel syndrome and improve the quality of life .