Abstract: To meet the needs for assembling, a kind of TE01 miter bend structure is designed and analyzed, which is composed of two perpendicular mode converting circular waveguides and a metal mirror that has a 45 angle with the center line of each circular waveguide. The whole structure is equivalent to a combination of two mode converting parts with a gap in the middle, where the length of the gap is equal to the diameter of the circular waveguide. The mode converting part converts TE01 mode into the mixed mode of TE01 and TE02, whose E-field has a symmetry distribution when propagating through the gap. As a result, the transmission loss is reduced and the efficiency is increased. A Ka band TE01 miter bend circular waveguide was designed, the simulation results obtained from CST match the measured results well. They both show that the transmission efficiency is above 98 % at the center frequency, the insert loss is below 0.2 dB and the VSWR is below 1.2 with the transmission efficiency greater than 95 % in 2 GHz band.