Abstract: This paper describes a wideband orthomode transducer (OMT) based on the ridged waveguide connection, the center frequency of OMT is 40 GHz, relative bandwidth is 50%. The transducer is aimed to work in Q-band receiver system in radio telescope. This OMT is composed of dual ridged waveguide connection joint, Y type joint and E type elbow, the structure of OMT is compact, and the influence of processing and assembling errors on the electrical performance is reduced. After testing the actual machining of the OMT, the reflection loss of Y type joint output S11 ≤ -22.7dB, the reflection loss of direct arm output ≤ -21.0dB, and the isolation between Y type joint output and direct arm output ≤ -43.4dB. The trend of curve change between actual measure and simulation result is very similar, and this OMT can satisfy the requirements of radio astronomic observation in (30~50) GHz bandwidth.