Objective To evaluate the ability of 3-AB to sensitize the human esophageal carcinoma cell strain (CaEs-17) to radiation in v/tro and its mechanisms. Methods CaEs-17 cells were treated with 3-AB at 0, 2.5, 7.5 mmol/L and given irradiation O, 3, 6, 9, 12 Gy. 3-AB concentration in each group was made dose-survival curve using multi-target single-hit maiths model by clonogenie assay. MTT assay was performed to observe the survival of irradiated cells.comet assay and metaphase chromosome analysis were used to measure the DNA damage degree and chromosome aberration of CaEs-17 cell after 3-AB treatment and irradiation. Results Cell survival experiments showed SER of 1.21, 1.52 for 2.5 mmol/L, 7.5 mmol/L 3-AB respectively using multi-target single-hit maths model. The survival fraction of irradiated CaEs-17 cell was decreased after 3-AB treatment. DNA damage and the chromatid breakage number of irradiated CaEs-17 cells were increased after 3-AB treatment. Conclusions 3-AB, a PARP inhibitor, can enhance the radiosensitivity of human esophageal carcinoma cell strain (CaEs-17). DNA damage repair inhibition by 3-AB might be one of the mechanisms.