The expression of the epidermal growth factor receptor (EGFR) contributes to radiosensitivity in several cancers, including rectal cancer. However, little is known about the mechanism underlying its radiosensitivity effect. To explore the mechanism, rectal cancer cell line HCT-15 with knockdown of EGFR was established through shRNA. The depletion of EGFR not only inhibited the cell proliferation and focus formation, but also induced cycle blockage of G0/G1 stage and enhanced radiosensitivity. In addition, the mRNA levels of key components involved in NHEJ pathway were significantly down regulated, including Ligase IV, DNA-PKcs and KU 80. EGFR- mediated NHEJ pathway may be involved in rectal cancer radiosensitivity.