As the development of terahertz communication technology, the research for 0.14 THz Folded Waveguide Traveling Wave Tube(FWTWT) requires higher power and wider band. RF characteristics changes of two-circuit folded waveguide slow wave structure are analyzed with different structure parameters for two-beam traveling wave tubes. The power divider and the power combiner of two circuits folded waveguide are analyzed and calculated. The efficiency of the combined power is about 96.3%. The interaction calculation model is established, including two circuits folded waveguide slow wave, the power divider and the power combiner, and the attenuator. Under the condition of voltage 15 kV and single beam current 40 mA, the combined output power is about 56 W in 0.14 THz frequency, and the gain is 31.4 dB, 3 dB wideband is 7 GHz.