Abstract: Objective：To study the relationship between the tyrosine kinases Etk/BMX and radiosensitivity in nasopharyngeal carcinoma (NPC) cells. Methods ： Recombinant plasmid pcDNA3.0-Etk was transfected into Sune-1, and Etk was highly expressed in the transfeced cell line Sune-wt.After 0, 2, 4, 10, 15Gy X ray radiation, MTT was used to measure survival fraction(SF) and flow cytometer (FCM) assay to examine cell apoptosis rate, cell cycle, proliferation index(PI), and apoptosis-related protein p53 and bcl-2. Results ：After different X ray radiations the survival fraction of Sune-wt were all higher than those of Sune-1 and Sune- vector(P＜0.05). The cell apoptosis rate of Sune-wt were all dramatically lower than those of Sune-1 and Sune-vector(P＜0.05).There was S,G2 phase blockage and highly up- regulated of proliferation index in Sune-wt after 15 Gy irradiation dosages.Moreover, there were significantly different expression of p53 and bcl-2 in Sune-wt after 15Gy irradiation (P＜0.05). Conclusion ：sThis study suggested that Etk/BMX played an important role in protecting nasopharyngeal carcinoma cells from X ray irradiation.Its mechanics may be ralated to p53 and bcl-2 changing and S,G2 phase blockage.