Time consuming of dynamic multileaf collimator(dMLC)quality assurance(QA)is an issue for clinical radiotherapy department.Considering the time consuming procedures in dynamic MLC QA,dedicated EPID based dynamic MLC QA program was widely used.It is kwon that Electronic portal imaging devices(EPID)for dMLC QA advantage is simple and quick set up,no need of separate system,high resolution,immediate analysis.Commercialized EPID based dMLC QA tool needs a validation of clinical site reference parameter.The purpose of this study is to validation of the EPID based QA tools for each dMLC QA category with the reference parameters and tolerance levels.We commissioned ARTSCAN TM(AQULLAB,Lille,France)for four Elekta Agility linear accelerator(Elekta AB,Stockholm,Sweden)MLCs and validated six category including calibration of image,dMLC dosimetry,static picket fence,VMAT picket fence,doe rate/gantry speed and MLC speed for dynamic MLC QA.We acquired 20 EPID images using vender provided dynamic delivery MLC file and validated it as an analysis protocol.We performed dMLC QA using same dynamic delivery MLC file for 6 month in the 4 Agility linac MLCs.The reference parameter was defined using 6 month average value and the tolerance level was defined using standard deviation value.We could see the meaning of the each category parameters and figure out each machines changing trend using ARTISCAN report tools after validation of each parameters.The EPID based dMLC QA tool not reduce the time consuming process,but also guaranties the dosimetric accuracy of dIMRT and VMAT by verification of MLC/gantry position and speed.