This paper presents a spreading model of momentum pitch ratio. The influence ofthe momentum pitch ratio spreading on interactive efficiency of the gyrotron with AQCORAA isstudied by the digital computation. The main conclusions are as follows:When the oblique angle ofAQCORAA is small
the interactive mechanism is CARM’ and the influence of momentum pitchratio spreading on interactive efficiency is stronger. When the oblique angle of AQCORAA is closeto 90"
the interactive mechanism is ECRM’ and the influence of momentum pitch ratio spreadingon interactive efficiency is weaker.