Abstract: The design methodologies, numerical results for TE₀₁ circular waveguide mode transducer were reported. It is shown that, TE₀₁ circular waveguide mode can realize high transmission efficiency in a wide band by utilizing travelling wave power divide structures, realizing TE₁₀ rectangular waveguide mode divided into four TE₁₀ rectangular waveguide modes, and then combining to a TE₀₁ circular waveguide mode. The optimized transducer has a transmission efficiency of over 99.9% at 9.40 GHz, and exceeds 99.0% in the range of 9.08-9.61 GHz. Experimental results show that the transmission loss is less than -0.2 dB, which is mainly caused by waveguide ohmic loss and waveguide-coaxial adapter. However, the results also have verified the feasibility of the manufactured transducer.