Abstract: The W-band receiver system can effectively receive many important spectral lines for radio astronomy observations, which is of great significance for astronomical observations and scientific research. As a crucial component of the receiver system, the W-band ortho-mode transducer is important to achieve polarization separation and it has a considerable impact on the overall performance of the receiver system. We design a W-band broadband OMT based on the Boifot junction and introduce the working principle and designing process of OMT. The simulation results show that the relative bandwidth of OMT reaches 49.4%, the return loss is better than 18.7 dB, the cross-polarization is better than 55.8 dB, and the port isolation is better than 54 dB in the 70-116 GHz band.