An in-line high efficient polarizer,composed of magnetic-ionic-liquid-adorned(MIL-adorned)hollow-core an-ti-resonant fiber(HARF),is theoretically proposed and experimentally demonstrated.The protocol is based on the se-lective conversion of polarization mode into leaky mode and attenuates quickly in MIL and the polarizer is featured by the magnetically tunable polarization extinction ratio(PER)and the thermally controllable operation bandwidth.