Abstract: Objective To investigate the effect of irinotecan （CPT-11） on radiosensitization and nuclear factor （NF）κB of esophageal cancer cells EC109. Methods MTT assay was used to observe the cell survival rates after treatment with different concentrations of CPT-11 （20， 50， 100， 200 μmol／L） for 24， 48 and 72 h as to screen the concentration with low cytotoxicity drug for subsequent experiments. According to the experimental design， the EC109 cells were divided into the control group， the irradiation group and the CPT-11+irradiation group. The survival fraction （SF） of different doses of Xrays （0， 2， 4， 6， 8 and 10 Gy） was detected by clone formation assay and the cell survival curve was calculated by using the multiple target model to calculate the enhancement ratio （SER）. The activation rate of caspase-3 and apoptotic rate were detected by flow cytometry after 48 h. Foci focus formation was applied to detect the DNA damage of each group. Western blotting was used to detect the protein level of NF-κB p65 and IκB-α in each group. The real-time quantitative polymerase chain reaction（qPCR） was applied to detect the Rad51 level in each group. Results CPT-11 in the range of 20～200 mol／L can decrease the proliferation rate of EC109 cells. The inhibitory effect was exerted in a dose and time dependent manner and the difference was statistically significant （P＜0.05）. Then， the concentration of CPT-11 close to 20% inhibition concentration（IC₂₀）（25 μmol／L） was selected in the following sensitivity test. The SFs of CPT-11+irradiation group were lower than those of the irradiation group， and the D0 of CPT-11+group was 1.39±0.14， lower than 2.46±0.17 of irradiation group with SER of 1.77. Compared with the control group and the irradiation group， the apoptotic rate， caspase-3 activation rate and the number of Foci focus were all increased， while the Rad51 level was decreased， and the difference was statistically significant （P＜0.05）. Compared with other two groups， there were lower level of NF-κB p65 and higher level of IκB-α in CPT-11+irradiation group （P＜0.05）. Conclusion CPT-11 can inhibit the proliferation， has the function of radiation sensitization and induce apoptosis of EC109 cells， which may be related to the inhibition of NF-κB pathway.