To observe the effects of Tong-Xie-Yao-Fang (TXYF) formula on movement index (MI, area under the curve of contraction intensity/min) and contraction frequency (CF, number of contractions/min) of experimental rats with diarrhea-predominant irritable bowel syndrome(D-IBS). Methods: The newborn Specific Pathogen Free(SPF) and Sprague-Dawley (SD) male pups were randomly divided into normal group, NMS+RS group and TXYF formula group. In addition to the normal group, D-IBS model with the method of neonatal maternal separation plus restraint stress (NMS+RS) were established in other two groups. On the 61st day, after the success of molding, normal group and NMS+RS group was given with saline, while TXYF formula group were given with 4.92 g/100 g TXYF formula. Three groups were dosed with the method of gavage with the drug delivery volume of 2 mL/100 g/d, for 14 consecutive days. The scores of Bristol classification and water content of the fecal pellets of rats were observed in the process of model building and dosing. The distinctions of movement index (MI, area under the curve of contraction intensity/min, mg/min) and contraction frequency (CF, number of contractions/min, times/min) of isolated colonic longitudinal smooth muscle strips (CLSMs) in three groups before and after treatment were observed with a Power Lab System. Results: Before treatment, scores of Bristol classification and water content of the fecal pellets in both TXYF formula group and NMS+RS group were all higher than that in normal group(P<0.05); After treatment, the scores of Bristol classification and water content of the fecal pellets in TXYF formula group were lower than that in NMS+RS group (P<0.01).Before treatment, the MI and CF of CLSMs in the NMS+RS and TXYF formula groups were similar and all higher than that in the normal group (P<0.01, respectively). After treatment, the MI and CF in the TXYF formula group was lower than in the NMS+RS group (P<0.01) and similar to the normal group (P>0.05). Conclusion: TXYF formula can effectively improve symptoms of D-IBS rats. Its mechanism may be achieved through Lower colon movement index and contraction frequency.