Objective:To investigate the effect and the mechanism of intragastric administration of gentamicin and lactulose on stress ulcer in rats with obstructive jaundice.Methods:Forty male Wistar rats were divided into 4 groups: Jaundice (Ligation of the bile duct) and intragastric administration of gentamicin and lactulose （group A）, jaundice with intragastric glucose（group B），sham operation with intragastris gentamicin and lactulose（group C）; and sham operation with intragastric glucose（group D）. Two weeks after the operation,the respective intragastric administration was given for 7 days,and then the water immersion and restraint stress induction procedures were performed in the 4 groups.Endotoxemia levels in portal vein were measured by the Limulus test and the ulcer index was calculated.Results:Group A showed significantly lower ulcer index and lower level of endotoxemia compared to group B,while the levels of endotoxemia and ulcer index in group B were increased, and group C and D also showed lower ulcer index and lower level of endotoxemia.Conclusions:Endotoxemia is an important aggravating factor for stress ulcer in obstructive jaundice.Intragastric administration of lactulose and gentamicin can decrease the level of endotoxemia which is beneficial to reduce the incidence of stress ulcer in rats with obstructive jaundice.