Objective To investigate the effect of TES gene on the radiosensitivity of nasopharyngeal carcinoma 5-8F cells. Methods Specimens of 5-8F cells (unprocessed group) and 5-8F cells with high TES expression (TES group) were irradiated at 0, 2, 4, 6, and 8 Gy radiation dose points.Cell clone formation experiment was conducted to draw the survival curve.Twenty-four BALB/c nude mice were randomly divided into four groups: nontransfection group, TES group, irradiation group, and TES irradiation group.A nude mouse model of nasopharyngeal carcinoma 5-8F cells was established.The length and diameter of the transplanted tumor were measured every three days, the tumor volume was calculated, and the growth curve of the transplanted tumor was drawn.After the mice were killed one month later, the tumor block was taken and weighed.The apoptosis of the transplanted tumor cells in each group was detected by flow cytometry. Results Compared with that in the unprocessed group, the survival rate of cells in the TES group was significantly lower (P < 0.01).The tumor growth rate and tumor mass of all four groups decreased in turn, while the apoptosis rate increased in turn.The TES irradiation group had the slowest tumor growth rate, greatest decrease in tumor weight, and highest apoptosis rate among the four groups.Multiple comparison revealed statistically significant differences between the groups (P < 0.05). Conclusion The testin gene can effectively improve the radiosensitivity of nasopharyngeal carcinoma 5-8F cells cultured in vitro.