Abstract: 　Objectives　To explore the clinical features of allergic colitis and the expression of eosinophil cationic protein (ECP) in intestinal mucosa in infant and young children. Methods　The clinical data of 24 cases of allergic colitis treated from September 2011 to February 2014 were analyzed retrospectively. Immunohistochemical staining was used to detect expressions of ECP in intestinal mucosa in 24 cases of allergic colitis, gastric and duodenal mucosa in 16 cases of helicobacter pylori infection and proximal normal intestinal mucosa in 18 cases of postoperative resection of congenital megacolon, and the results were compared. Results　In the 24 subjects (15 males and 8 females) with allergic colitis,. they were infants except for 1 subject, and 20 subjects were <6 months old. All of them had bloody stool, in which there were 15 cases of diarrhea, 1 case of eczema and 3 cases of drug allergy. The endoscopic lesions were mainly showed in the sigmoid colon (12 cases) and the rectum (11 cases). The most common manifestations were mucosal erythema (21 cases), pox like nodules (18 cases), erosions (3 cases), and ulcers (3 cases). Histopathological findings were eosinophilic infiltration of the mucosa. The number of eosinophils in intestinal mucosa was 42 (30~60) in patients with allergic colitis whose ECP was positive, 18 (15~23) in patients with Helicobacter pylori infection and 25.5 (14~35) in patients with congenital megacolon children,  and the differences are statistically significant mong three groups (H=28.14， P<0.001). Conclusions　Allergic colitis is more common in infants and young children. The main endoscopic findings are mucosal erythema and eruption like nodules. In addition, the increase of ECP positive eosinophils in intestinal mucosa is the characteristic manifestation of allergic colitis.