The 60-GHz traveling-wave tube(TWT) prevails nowadays as the amplifier for the satellite communication and electronic countermeasures.The folded waveguide(FW) is a promising all-metal slow-wave structure(SWS)for the 60-GHz TWT with advantages of robust performance,fine heat dissipation,considerable power and bandwidth.A novel FW periodically loaded with rectangular grooves is analyzed for the purpose of gaining higher power and gain.The rf characteristics are investigated by numerical simulation,and the nonlinear largesignal performance of such a TWT is analyzed by a 3D particle-in-cell code MAGIC.Compared with normal circuits,relatively higher continuous-wave power(40-56 W) and similar bandwidth(5 GHz) are predicted by simulation.Meanwhile,the designed operation voltage is 10.5kV,which keeps the low-voltage advantage of the popular helix TWT competitor.The novel FW will favor the design of a broadband and high-power 60-GHz TWT. The 60-GHz traveling-wave tube (TWT) prevails nowadays as the amplifier for the satellite communication and electronic countermeasures. The folded waveguide (FW) is a promising all-metal slow-wave structure (SWS) for the 60-GHz TWT with advantages of robust performance, fine heat dissipation, considerable power and bandwidth. A novel FW slowly loaded with rectangular grooves is analyzed for the purpose of gaining higher power and gain. rf characteristics are investigated by numerical simulation, and the nonlinear largesignal performance of such a TWT is analyzed by a 3D particle-in-cell code MAGIC. Compared with normal circuits, relatively higher continuous-wave power (40-56 W) and similar bandwidth (5 GHz) are predicted by simulation. is 10.5 kV, which keeps the low-voltage advantage of the popular helix TWT competitor. The novel FW will favor the design of a broadband and high-power 60-GHz TWT.