Objective To study the animal model of intestinal mucositis induced by 5-fluorouracil(5-FU) in mice. Methods The different doses of 5-FU were intraperitoneally injected into mice by 1 day or 5 consecutive days. The body weight,diarrhea score and food intake of mice were recorded daily, and peripheral blood and small intestine tissue?morphological?change?were detected after the last administration of 24 h or 72 h. Results Compared with the control group, after administered 5-FU, Each dosage groups showed various degrees of body weight loss,diarrhea and reduce?of?food intake,white blood cell and platelet counts in peripheral blood decreased significantly(P<0.05 or P<0.01). And the small intestine demonstrated evident pathological characteristic at the single dose of 400 mg?kg-1 and the continuous injection of 50 mg?kg-1, 100 mg?kg-1, but the mortality rate was 100% due to the high dose in the 100 mg?kg-1group. Conclusions The effect of 5-FU in inducing intestinal mucositis in mice by 1 day or 5 consecutive days of injection is correlated with the dosage. The model can be induced by single dose of 400 mg?kg-1 or 50 mg?kg-1 for 5 consecutive days .