Abstract: Toll-like receptor 4(TLR4)is an important group of pattern recognition receptors, which is expressed not only on immune cells widely, but also on a variety of tumor cells. TLR4 can promote the development and progression, immune escape, apoptosis resistance, metastasis and invasion of tumors through different signal transduction mechanisms. Activated TLR4 plays an important role in the tumor microenvironment, and its influence on the radiosensitivity of tumor cells reduces the effect of radiation therapy severely. The study of these mechanisms can further identify the target for cancer radiotherapy, which will undoubtedly provide a new method for the treatment of malignant tumor.