Abstract: A majority of the high power microwave reflector antennas, which work at high frequency band, employ beam waveguide as feed line. The traditional high power beam waveguide is fed by a high power horn, whose volume is much huger and that the first mirror of the beam waveguide is large. A novel X-band high power microwave feeder with polarization reconfigurable capacity was proposed and simulated. Two phase-correct mirrors were used to transform high power microwave beam to the desired beam, so as to increase power capacity of the window. Two cascaded circular grates were employed to control the polarization of the output beam. And simulation of the feeder was laid out to check the aforementioned design.