Objective To investigate the effect of small interfering RNA (siRNA) interference in the expression of epidermal growth factor receptor (EGFR) on the radiosensitivity of esophageal squamous carcinoma (Eca-109) and esophageal adenocarcinoma (OE-19) cell lines.Methods Human Eca-109 and OE-19 cell lines were selected as study subjects.Various EGFR-siRNA and negative siRNA were synthesized chemically through lipofection.Reverse transcription-polymerase chain reaction and Western blot were applied to measure the expression of EGFR before and after transfection,and the CCK8 assay was applied to analyze the influence of transfection on cell proliferation.Blank control groups of Eca-109 and OE-19 cells (O1 and O2 groups),simple irradiation groups (R1 and R2 groups),and EGFR-siRNA irradiation groups (E-R1 and E-R2 groups) were set,and the doses for single irradiation were 0,2,4,6,and 8 Gy.The colony-forming assay was applied to calculate survival fraction (SF) and sensitization enhancement ratio (SERD0 ratio),and flow cytometry was applied to evaluate the influence of EGFR-siRNA combined with radiotherapy on cell cycle distribution and apoptosis rate,and the dose for single irradiation was 6 Gy.Results The expression of EGFR in both cell lines was significantly down-regulated by EGFR-siRNA,and the inhibition rate of cell proliferation by transfection was＜5％ (4.9％ and 4.5％,respectively).The results of colony-forming assay showed that the cells in the E-R1 and E-R2 groups had a lower SF than those in the O1 and O2 groups,with an SERD0ratio of 1.40 and 1.01,respectively.The results from flow cytometry showed that compared with the E-R2 group,the E-R1 group had a higher proportion of cells in G2/M phase and a lower proportion of cells in S phase after irradiation (P=0.016 and 0.028),as well as a higher apoptosis rate (P=0.007).Conclusions Compared with the cell line OE-19,the cell line Eca-109 has a significantly increased radiosensitivity when treated with siRNA interference in EGFR expression.