Abstract: In high power microwave transmission systems, over-mode waveguides are often used to improve power capacity and efficiency, thus the mixed modes of TM₀₁ and TE₁₁ often appear in circular waveguides. In this paper, the method of extracting the mixing ratio and polarization angle of the TE₁₁ mode is analyzed and studied by using an 8-hole circular waveguide coupler with uniform angular distribution. The electric field distribution of the TM₀₁ and TE₁₁ modes in the circular waveguide at the coupling hole is analyzed, and the output power of each coupling hole is simulated by CST. By obtaining the average power of the coupling holes facing each other and the average power of the eight holes, it is concluded that the ratio is independent of the phase difference between the modes. At the same time, it is found that the ratio is linearly related to the mixing ratio of the TE₁₁ mode, and the proportionality coefficient in the linear relationship is a linear function of the polarization angle. Expressions for calculating the TE₁₁ mode mixing ratio and polarization direction are obtained by linear fitting. Compared with the parameters set by the simulation, the results calculated by this expression show that when the mixing ratio of TE₁₁ mode is less than 30%, it is feasible to use it to calculate the mixing ratio and polarization angle of TE₁₁ mode, and the error does not exceed 10%. On this basis, this paper presents a specific method for judging TE₁₁ mode information in practical situations.