Abstract: The disadvantages of the uniform slowwave structure in Cerenkov beamwave interaction are analyzed. It is put forward that in the sectional slowwave structure, the drift tube and the two section SWSs of its ends comprise a Bragg resonant cavity, which can reduce the energy dispersal of the modulated beam electrons due to the transit time effect when the length of the drift tube is well chosen, thus to enhance the beamwave energy conversion efficiency. By means of the PIC simulation, physical graphs of beamwave interaction in the uniform slowwave structure case and in the sectional slowwave structure case are compared, and the simulation results confirm that the latter has several advantages, such as more effective beamwave energy conversion efficiency, better spectrum qualit