Abstract: OBJECTIVE To explore the acupuncture treatment mechanism of constipation-predominant irritable bowel syndrome(IBS-C) from the perspective of brain-gut axis， by observing the plasma 5HT， CGRP and NPY level before and after the treatment. METHODS 60 patients with IBS-C were randomly divided into two groups. 30 cases in the acupuncture group(AG) were treated by acupuncture five times a week， with such acupoints as Tianshu， Zusanli， Shangjuxu， Taichong， Sanyinjiao， Yintang， Baihui being selected. The other 30 cases in the medicine group(MG) were treated with lactulose oral solution， 15 ml per time for three times a day. After 4 weeks treatment， enzyme-linked immunosorbent assay (ELISA) was used to detect the plasma 5HT， NPY and CGRP level of 30 healthy volunteers and the two treatment groups and observe the improvement of clinical symptoms. RESULTS ①Both groups could significantly improve the clinical symptoms in patients with IBS-C (P<0.01)，while the curative effect in the AG was superior to that in the MG (P<0.01). ②The levels of 5-HT， NPY and CGRP in patients with IBS-C of two treatment groups were significantly higher than those in healthy volunteers， and the difference was statistically significant (P<0.01). The plasma 5-HT， NPY and CGRP levels all went down in both groups after treatment， and the differences of 5-HT， NPY and CGRP levels were significant when compared to the levels before treatment in AG(P<0.01). The differences of 5-HT，NPY levels were also significant when compared to the levels before treatment in MG(P<0.01)， while there was no significant difference on CGRP(P<0.01). There were no significant differences of 5-HT and NPY levels between these two groups after treatment (P>0.05)， but the difference of CGRP was highly statistically significant(P<0.01). The downward trend of 5-HT，NPY and CGRP level was better in the AG. CONCLUSION ①Acupuncture treatment can significantly improve the clinical symptoms in patients with IBS-C， and the theraputic effect is superior to that in the MG. ②The increase of 5-HT， NPY and CGRP level in patients with IBS-C after treatment suggests a close relationship between the abnormal level of brain-gut peptide and IBS syndrome. ③Acupuncture treatment can decrease the plasma levels of 5-HT， NPY and CGRP， alleviate the degree of abdominal pain and discomfort， which indicates that benign regulation of brain-gut peptide level in patients with IBS-C by acupuncture may be one of the effective mechanisms in treatmenting this disease.