Abstract: The dynamic dispersion equation of Gyro-TWT is analyzed in this paper. The dependences of the coupling coefficient of beam-wave interaction on the parameters of electron beam are simulated and discussed. The results are helpful to the optimizations of the parameters of electron beam, which could enhance the performance of a Gyro-TWT. The electrons employed in this paper distribute along some circles uniformly, which centers locate at one same circle. The cylindrical waveguide has a uniform section.