Abstract: A cold and uniform plasma-filled traveling wave tube with sinusoidally corrugated slow wave structure is driven by a finite thick annular intense relativistic electron beam and the entire system is immersed in a strong longitudinal magnetic field. By means of the linear field theory, the dispersion relation for the traveling wave tube RTWT is derived. The dispersion characteristic of the RTWT is analyzed by numerical computation. The trend of the change for gain, bandwidth and center frequency of the RTWT is discussed in detail in different kinds case which include density of plasma, transmission place of electron beam, voltages as well as current. Some useful results are obtained on the base of the discussion.