Abstract: The multileaf collimator (MLC) to achieve beam-intensity modulation is used more and more in most radiotherapy center. The various approaches to modulation have been developed that use the motion of the MLC leaves during irradiation to create a dynamic compensating filter either for a number of fixed gantry exposures or for a continuous arcing fan beam and for a continuous arcing cone beam. In order to obtaining much better therapeutic effect, we must have a strict scientist quality assumance(QA) and quality control(QC) management of MLC in intensity modulated radiation therap.