Abstract: Objective: To screen the Lactobacillus acidophilus of the high resistance against gastro-intestinal tract from three Lactobacillus acidophilus and study it's immunomodulating effect on artificial ulcerative colitis mice.Methods: The environment of gastric juice,intestinal juice and bile salt were simulated,different concentration were set,and survival rates of three Lactobacillus acidophilus in the environment of gastric juice,intestinal juice and bile salt were studied to reflect the resistance against gastro-intestinal tract of human.Lactobacillus acidophilus with a high resistance to the gastrointestinal tract was studied as the object,and mice from the treated groups were freely drunken 3% dextran sulfate sodium salt( DSS) solution for 7 days and were studied as the animal model to study the anti-colitis potential.Results showed that,when the p H of stomach acid was at 2.5~4.5,the bacterial count of Lactobacillus acidophilus CGMCC10436 was greater than 107 CFU/mL,and there was no downward trend at 3 h. In the environment of intestinal juice for 2 h,the bacterial count of Lactobacillus acidophilus CGMCC10436 was greater.At a concentration of 4 g/kg in the environment of bile salt,the bacterial count is greater than the1 × 107 CFU /mL at 3 h. Lactobacillus acidophilus CGMCC10436 had high resistance against gastro-intestinal tract,and 3 ×108CFU Lactobacillus acidophilus CGMCC10436 could have anti-inflammatory effect,repaired the injury of intestinal mucosa and enhanced immune regulation.