The invention discloses a device and method for reducing passive intermodulation of a coaxial filter, and relates to the field of microwave wireless communication. The device comprises a frequency modulation part, a coupling adjustment screw, a metal cover plate, a metal cavity body and a resonant rod. Passive intermodulation generation positions comprise a frequency modulation position, a coupling adjustment screw position, a connection position of the coaxial resonant rod structure with the metal cavity, a connection position of the metal cavity and a connection position of the metal cover plate with the metal cavity. The metal-non-conductive medium-metal contact is realized by a non-conductive medium, and the high-voltage contact between the metal cover plate and the metal cavity is realized by the pressure-increasing ring, thereby realizing the inhibition of the passive intermodulation caused by the coaxial filter. The device has the advantages of simple structure, light weight, short design period and low design cost. The device and method can be widely applied to the aerospace field and the ground communication field.