ObjectiveTo study the function of Beclin1 on the radioresistance in nasopharyngeal carcinoma．MethodsWestern blotting was used to check the Beclin1 protein in CNE2, 610B and their radioresistant cell lines CNE2Rs, 610BRs,as well as the dynamic changes of Beclin1 protein in CNE2 cell exposed to irradiation under different conditions. Plate colony formation assay was applied to examine the alterations of radioresistant capacity in CNE2 and 610B after the expression of Beclin1 was upregulated with Lipofectaminemediated Beclin1 cDNA and inhibited with lentivirusmediated Beclin1 shRNA．Immunofluorescence was adopted to detect the expression of γH2AX，which was a surrogate marker of DNA doublestrand breaks．ResultsThe expression of Beclin1 protein was increased in radioresistant cell lines and after irradiation，which displayed an irradiation dosedependent and timedependent manner．Beclin1 overexpression in 610B cells resulted in enhanced ability to form colony on plate and high survival fraction, increased γH2AX foci formation. On the contrary，inhibition of Beclin1 expression in CNE2Rs cells led to declined ability of plate colony formation and low survival fraction, decreased γH2AX foci formation．ConclusionBeclin1 promotes radioresistance of nasopharyngeal carcinoma, which may be related to modulating the repair process of DNA doublestrand breaks．