OBJECTIVE： To observe the improvement effects of Wenwei tiaochang granule on constipation-predominant irritable bowel syndrome （IBS-C） model rats， and to discuss its mechanism. METHODS： 60 SD rats were randomly divided into normal group， model group， mosapride group （positive drug， 50 mg/kg） and Wenwei tiaochang granule low-dose， medium-dose and high-dose groups （3， 6， 12 g/kg）， with 10 rats in each group. Except for normal group， other groups were given ice water mixture intragastrically to induce IBS-C model. After modeling， treatment groups were given relevant medicine intragastrically， and normal group and model group were given constant volume of normal saline intragastrically， once a day， for consecutive 14 d. After medication， 24 h dejection amounts and water rate of manure were measured. The serum contents of 5-HT and CGRP were determined by ELISA. RT-PCR and Western blot assay were used to determine mRNA and protein expression of SERT and CGRP in colon tissue. RESULTS： Compared with normal group， 24 h dejection amounts and water rate of manure were decreased in model group， serum contents of 5-HT and CGRP were increased， and mRNA and protein expression of SERT and CGRP in colon tissue were also increased （P＜0.05 or P＜0.01）. Compared with model group， above indexes of treatment groups were all improved to different extent， with statistical significance （P＜0.05 or P＜0.01）， except the decrease of mRNA expression of SERT in colon tissue was not significant in Wenwei tiaochang granule low-dose group. CONCLUSIONS： Wenwei tiaochang granule can improve the dejection and symptoms of constipation in IBS-C model rats， which maybe associated with decreasing the levels of 5-HT， CGRP and other neurotransmitter in serum and intestinal tissue.