Abstract: An electron beam was regarded as a plasma column, and the eigen frequency equations of the TM0m0 mode of a cylindrical cavity filled with a plasma column in the center are deduced based on the analytic method in this paper. It is studied in detail that the resonant frequency and the electromagnetic field distribution of the TM010 mode and the TM020 mode changes with the plasma frequency of the electron beam. The research results show that the resonant frequency of the TM010 mode and the TM020 mode will increase with the increasing of the plasma frequency of the electron beam, and the distribution of the electromagnetic fields also changes. When the electron beams plasma frequency exceeds the resonant frequency of the cavity, the electromagnetic field distribution of the TM010 mode and the TM020 mode in the cylindrical cavity will change greatly, and some peculiar phenomena will appear, such as the electric field inside the electron beam will be in the opposite direction of the electric field outside the electron beam, the electromagnetic field will be converged on the brim of the electron beam, and so on.