The paper mainly presents the design of beam-wave interaction of a C-band high-peakpower high-efficiency broadband klystron.The beam-wave interaction section is designed based on considerations of efficiency and bandwidth synthetically.As a part of beam-wave interaction section,buncher section is simulated by Particle-In-Cell(PIC) code to observe the bunching process of electron beam to achieve high conversion efficiency of electron beam and RF field.When it comes to the other part,output circuit is designed as a three-section filter by an output cavity loaded with Chebyshev filter,and the cold test results are given.The beam-wave interaction is simulated by EGUN code and Arsenal-MSU code respectively.The simulated results indicated that,the existence of power dips in the operating bandwidth is verified by Arsenal-MSU code,comparing proper results by EGUN code.Then,the method that design parameters are not adjusted except parameters of buncher cavities to remove potential power dips is described.What is more,the simulated results of electron optics system are given by EGUN code and Arsenal-MSU code respectively.The further hot test results of klystron prove that the whole design of beam-wave interaction is effective. The paper mainly presents the design of beam-wave interaction of a C-band high-peak power high-efficiency broadband klystron. The beam-wave interaction section is designed based on considerations of efficiency and bandwidth synthetically. As a part of beam-wave interaction section, buncher section is simulated by Particle-In-Cell (PIC) code to observe the bunching process of electron beam to achieve high conversion efficiency of electron beam and RF field.When it comes to the other part, output circuit is designed as a three-section filter by an output cavity loaded with Chebyshev filter, and the cold test results are given. The beam-wave interaction is simulated by EGUN code and Arsenal-MSU code respectively. The simulated results indicated that, the existence of power dips in the operating bandwidth is verified by Arsenal-MSU code, comparing proper results by EGUN code. Chen, the method that design parameters are not adjusted except parameters of buncher cavities to remove potential power dips is the simulated results of electron optics system are given by EGUN code and Arsenal-MSU code respectively. The further hot test results of klystron prove that the whole design of beam-wave interaction is effective.