Objective To establish an animal model of gastrointestinal microflora imbalance induced by an antibiotics,ceftriaxone.Methods Specific-pathogen-free mice received orally antibiotics in the drinking water ad lib(the concentration was 0.5 mg/mL),or via intragastrical gavage in a dose of 125 mg/mL,0.2 mL b.i.d.for 4 days.On the 5th day,the mice were sacrificed and intestinal flora analysis was performed.Results Both the two methods induced alteration of intestinal flora,but the intestinal mucosa of mice treated by intragastrical gavage showed more rapid repair and the translocation of bacteria was lower than that in the mice of group administered with antibiotics in drinking water.Conclusion Administeration of ceftriaxone in drinking water ad lib is a perfect method to induced intestinal microflora dysbiosis in mice.