Abstract: Objective： To study the expression of mediator of the MDC1 and 53BP1 mediators in esophageal carcinoma cells after ⁶⁰Co γ-rays irradiation in vitro. Methods：Expression of MDC1 and 53BP1 proteins were detected by Western blot after different time points with 1,2,5,10Gy in TE-13 and ECA109 esophageal carcinoma cells in vitro, ECA109 cell was collected 1h after different irradiation dosages (0, 2, 4, 6, 8 and 10 Gy) and different time points (5,15, 30, 60, 120 and 240 min) after 4 Gy of γ-irradiation, the immunofluorescence images were taken under a Zeiss fluorescence microscope. Results：The expression of MDC1 and 53BP1 proteins in TE-13 and ECA109 cells has no significant change at 1h, 2h and 24 h after irradiation with 1,2,5,10Gy (P>0.05); MDC1 and 53BP1 foci were evident 5 min after exposure to 2Gy IR.The number of foci increased gradually with the increase of the IR dose (P<0.05). The time course of MDC1 and 53BP1 foci formatited and dispersed after exposure to 4Gy-IR had been investigated. MDC1 and 53BP1 foci were evident at the earliest time point examined, 5 min after irradiation. The average number of foci per cell peaked at the 30 min(MDC1) and 1 h(53BP1) time point, the average number of foci were 26.3 and 36.7 respectively.After that,the MDC1 and 53BP1 foci began to disperse, gradually, the number of foci per cell returned to baseline levels 4 h after irradiation.Compared with the control group, there have remarkable difference in the average number of foci of MDC1 and 53BP1(P<0.05). Conclusion ：Irradiation can affect the number of gene MDC1 and 53BP1 nuclear foci but not expression of MDC1 and 53BP1 protein in esophageal carcinoma cells.