Abstract: In response to the future deep space exploration and manned lunar landing engineering requirements in China, it is necessary to expand the Ka-band tracking and control capabilities of the 35 m deep space tracking and control system. This paper proposed a high-power wide-passband dichroic mirrors for Ka-band. The dichroic mirror consists of rectangular aperture units arranged in a triangular periodic pattern, transmitting the Ka-band, reflecting S-band and X-band, and using a pure metal structure to adapt to the long-term operation of high-power feed sources. The simulation and measurement results show that the designed dichroic mirror has a wide-passband and low insertion loss characteristics, with transmission loss less than -0.47 dB in the 22.5 GHz~ 27.0 GHz, less than -38 dB in the 7.0 GHz~8.5 GHz, and less than -53 dB in the 2.0 GHz~2.3 GHz. It is suitable for application in the 35 m beam waveguide(BWG) antenna of deep space telemetry tracking and command(TT&C) system.