Abstract: In order to solve the problem of insufficient spectrum coverage in the next generation ultra-wideband detection or radar system at millimeter wave band, a W-band broadband waveguide duplexer is proposed, which can effectively realize the separation or combination of two broadband spectrum signals. In this article, the architectural design of waveguide duplexer based on the waveguide hybrid network principle is proposed. Then, the waveguide duplexer at full W-band is designed and optimized, combining with the high-pass filter. This duplexer can not only achieve the performance of wideband frequency division/ frequency combination and high isolation, but also can maintain a simple structure that is easy to be processed in the high frequency band. Finally, this W-band duplexer can be machined by using the computer numerical control (CNC) technology. The practical results show that this duplexer can divide the full W-band into two frequency bands of 75- 94 GHz and 94 - 1 1 0 GHz ( 3 dB FBW is 2 2 . 6 % and 1 5 . 7 % respectively ) . The insertion losses in two channels are about -0. 5 dB and -0. 6 dB respectively. The isolation degree between two channels is mainly better than -15 dB. And the above measured performance agrees well with the simulation data. In addition, such W-band waveguide duplexer with a simple structure can be easily scaled up to terahertz high-frequency applications.