Abstract： Objective To investigate the influence of vasoactive intestinal peptide （VIP) on the sling fibers and the clasp fibers of the lower esophageal sphincter （LES） and the difference， and explore whether VIP belongs to a nonadrenergic and noncholinergic （NANC） neurotransmitter. Methods Thirty LES specimens were obtained from 30 patients with high-position carcinoma of the middle thoracic esophagus who underwent esophagectomy from March to August 2010 in Fourth Affiliated Hospital of Hebei Medical University. There were 14 male patients and 16 female patients with their average age of 58.0±6.1 years. The clasp fibers and sling fibers were isolated and suspended in perfusion. Exogenous VIP was added to the two kinds of strips to draw a concentration-effect curve. Electric field stimulation （EFS） or exogenous VIP was applied to clasp fibers and sling fibers， and the influence of VIP （10-28） on LES was compared. Results ExogenousVIP in different concentration caused concentration-dependent relaxation of the sling fibers and clasp fibers of LES in vitro. There was statistical difference in relaxation between the sling fibers and clasp fibers under same VIP concentration （P＜0.05）， and the relaxation of sling fibers was more significant than that of clasp fibers. VIP （10-28） transiently inhibited the relaxationof the sling fibers and clasp fibers caused by exogenous VIP. VIP （10-28） also transiently inhibited the relaxation of the sling fibers and clasp fibers after the activation of EFS. Conclusion The relaxation of sling fibers and clasp fibers induced by EFS is related to VIP. VIP is a kind of NANC neurotransmitter in human LES.