Ulcerative colitis (UC) is an inflammatory destructive disease of the large intestine occurred usually in the rectum and lower part of the colon as well as the entire colon. In this paper, the influence of IL-1α and IL-4 on the experimental ulcerative colitis by light emitting diode ( LED ) (λ: 632.8nm; power: 4.0mw) applied to colon directly were studied. Making 30 rats into 3 groups: LED curative group, model group, normal control group. There were 10 rats of each group. We used glacial acetic acid (5%) and trinitro-benzene-sulfonic acid (TNBS) (1%) intra-anally to replicate the rat model of ulcerative colitis. After a week treatment with administrating LED rectal irradiation to curative group, 30mm each time, once per day, the histopathological studies in colonic tissue were performed, and the expression and distribution of IL-lα and IL-4 in colonic tissues were investigated by immunohistochemical staining. The extent of the Colonic tissue injury in LED curative group was not as significant as that in the model group. Compared with model group, the content of MDA in LED curative group was reductived and the activity of SOD was increased significantly, and the expression and distribution of IL-lα in LED curative group was depressed significantly, however the expression and distribution of IL-4 in LED curative group was increased obviously. This results show that the LED rectal irradiation can protect colonic mucosa from the experimental ulcerative colitis in rats, and suggest that the effects may be related to the photobiomodulation and immunomodulation of LED.