Stress ulcer occurs primarily in severe conditions, with a high incidence and mortality in intensive care units. However, studies on the association between stress ulcer and bile reflux to the stomach with stress ulcer are still inconclusive. Therefore, our research aimed to determine whether or not bile reflux exists during stress ulcer and then to investigate the effects and mechanism of changes of pyloric local neurotransmitters on bile reflux in such circumstances so as to provide a new pathway for clinical intervention. Cold water immersion was used to copy the stress ulcer model of rats. Sixty-five adult Sprague-Dawley rats of either sex were randomly divided into three groups: the normal control group (n = 10), the stress group (n = 30), and the antagonist group (n = 25). The gastric ulcer index, pH, and bile acid of gastric juice were measured before and after stress. Radio Immunoassay Detection Kit and Biochemic Detection Kit were used to measure local contents of CGRP (calcitonin gene-related peptide) and nitric oxide, respectively, in rats' pylorus. The local contents of nitric oxide in rats' pylorus reached a maximum at 1 hr after stress. The bile acid and pH of gastric juice peaked at 2 hr after stress and the ulcer index peaked at 4 hr after stress. But the local contents of CGRP in rats' pylorus decreased to the minimum at 4 hr after stress. The bile acid and ulcer index in the L-NAME group were significantly lower than in the antagonist control group. However, the bile acid in the hCGRP8-37 group was less than in the antagonist control group. Compared with hCGRP8-37 group, there was a significant reduction in bile acid in the L-NAME group. There was a significant reduction in the ulcer index of the hCGRP8-37 group compared with the L-NAME group and the antagonist control group. There was a certain kind of positive correlation between nitric oxide in rats' pylorus and bile acid to the stomach, for nitric oxide could loosen the pyloric sphincter and increase the bile acid to the stomach. L-NAME might reduce the local nitric oxide contents in rats' pylorus so that bile acid to the stomach might be decreased, obviously with a looser tight pyloric sphincter. Meanwhile, the CGRP in rats' pylorus was negatively associated with the ulcer index, hence CGRP might protect gastric mucosa under stress conditions.