〔Abstract〕 Objective To explore the mechanism of modified Tuoli Xiaodu powder in the treatment of radiation proctitis based on TLR4/NF-κB signaling pathway. Methods Forty-eight SD rats were randomly divided into 6 groups, except for the control group, all the other groups were induced to make the rat model of radiation proctitis. After 3 d of normal feeding, the rats began enema, the control group and model group were enema with 2 ml 0.9% normal saline, and the positive control group were treated with 2 ml montmorillonite powder(0.2 g/ml) combined with dexamethasone(1 mg/ml) enema, modified Tuoli Xiaodu powder 2 ml enema with low(1 mg/ml), medium(2 mg/ml) and high dose(4 mg/ml) was performed once a day for 10 d. Then rats were killed, the diameter of rectum was measured, the histopathological changes of rectum were observed by HE staining, the levels of serum interferon-γ(IFN-γ), tumor necrosis factor-α(TNF-α), interleukin-4(IL-4), IL-10, epidermal growth factor(EGF) and IgA, IgM and IgG were measured by ELISA, the expressions of TLR4, Myd88, NF-κB p65, IκBα in rectum were detected by Western blot, and the expressions of TLR4, Myd88, NF-κB p65, IL-6 and IL-10 mRNA in rectum were detected by qRT-PCR. Results High dose of modified Tuoli Xiaodu powder could significantly improve the pathological changes of rectal tissue and reduce the score of rectal inflammation(P<0.05). Compared with the model group, the high dose of modified Tuoli Xiaodu powder could significantly increase the levels of serum EGF, IL-4, IL-10, IgA, IgM and IgG(P<0.05). The expression of IFN-γ, TNF-α, TLR4, Myd88, NF-κBp65, IκBα and TLR4, Myd88, NF-κBp65 and IL-6 mRNA significantly decreased in rats(P<0.01). Conclusion The high dose of modified Tuoli Xiaodu powder can significantly improve the pathological changes of rectum in rats with radiation proctitis and play a significant role in the expression of TLR4/NF-κB signaling pathway related factors and inflammatory cytokines.