To investigate the antidiarrheal mechanism of quercetin extracted from Psidium guajava L.The effects of quercetin on the contractility of guinea pig ileum in vitro and on the peristaltic motion of mouse small intestine in vivo were observed, and the peak value of contractility and peristaltic distance recorded. The inhibitory effect of quercetin on the permeability of the abdominal capillaries was also observed.Quercetin inhibited the contraction of guinea pig ileum in vitro and the peristaltic motion of mouse small intestine, and reduced the permeability of abdominal capillaries.Quercetin can inhibit the intestinal movement and reduce capillary permeability in the abdominal cavity, which may be the antidiarrheal mechanism of Psidium guajava L extract.