The invention provides a high and low frequency oscillator coaxial installation platform, which comprises an installation base and an isolating reflection piece arranged on the installation base, wherein the isolating reflection piece is cross-shaped and comprises a central part and extending parts extending from the periphery of the central part in four directions, each extending part extends obliquely upwards, and there is an included angle between a plane at which each extending part is located and a plane at which the central part is located. The high and low frequency oscillation coaxialinstallation platform is basically in the shape of a cross-shaped thin piece bending upwards. Low-frequency cross polarization electromagnetic waves are converted into low-frequency principal polarization electromagnetic waves through the high and low frequency oscillation coaxial installation platform. Meanwhile, high and low frequency oscillation coaxial installation platform realizes isolationfor high and low frequency electromagnetic waves; wave beams radiated by a high-frequency oscillator tend to be consistent in axial propagation distance after being reflected by the cross-shapedextending parts, thereby achieving greater gain, having the functions of low-frequency orthogonal mode conversion and high-frequency gain promotion. The high and low frequency oscillator coaxial installation platform not only is a high-frequency reflector and has the functions of isolating the low-frequency oscillator and improving the dispersion of high-frequency wave beams, but also is a low-frequency polarization separation piece and has the functions of improving the low-frequency cross polarization discrimination rate and improving the low-frequency gain.