A novel slow wave structure with dual-gratings in parallel based on staggered double channels is proposed. The structure formed by double beams and a focusing system has a two-dimensional structure. Dispersion characteristics of slow-wave structure are simulated and analyzed in detail. The high frequency structure consists of power dividers and transmissions, and its output ports are standard waveguide named WR-2.8. The transmission losses of the whole RF structure S21＞?4.4 dB and the reflection parameter S11＜?15 dB are achieved. The beam-wave interaction properties of single channel and double channels are also simulated, and the gain can reach 14.586 dB with a current density of 53.57 A/cm2. Because of lower current density and simple structure, the RF system shows the application potential for terahertz Traveling Wave Tube(TWT).