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Objective To compare the dose verification between 6X and 6X flattening filter-free(6FFF) in volumetric modulated arc therapy (VMAT) for the treatment of nasopharyngeal carcinoma(NPC)，and verify the clinical feasibility of 6FFF VMAT plan. Methods The two dimensional ionization chamber matrix Array729 and OCTAVIUS Octagonal phantom from PTW Company were used to verify the 6X and 6FFF VMAT plan of 15 patients. Results Gamma 2D analysis criteria was used to evaluate the verification results (standard error as 3mm and 3%)，the pass rate of local dose method for 6X was (95±3) %，while the max dose method was (96±3) %. For 6FFF，local dose method was (94±3) %，and max dose method was (95±3) %. Conclusions PTW Array729 can be used for clinical validation of 6X and 6FFF VMAT plans，the pass rate of 6FFF plan is lower than that of 6X plan，P>0.05 for local dose，and P<0.01 for max dose. The pass rate of local dose method is less than max dose (P<0.001) in the dose verification result for the same plan.