A dual-beam rectangular ring-bar （DBRRB） slow wave structure （SWS）， which is with a planar structure and is suitable for micro fabrication， is proposed for W-band traveling-wave tubes （TWT）. Supported by a pair of T-shaped dielectric rods， the RRB SWS is fit for dual-sheet beam operation. The high frequency characteristics are analyzed by using computer simulations. Wide bandwidth input-output structures adopting tapered structure and step waveguide are designed. Hot-test performance of the RRB SWS is investigated by means of Particle-in-cell （PIC） simulations. A solenoid magnetic field of 0.6 T is adopted to focus the sheet beams with voltage and current of 11.2 kV and 0.12 A. The saturated output power of 56.7 W at 94 GHz is obtained at the output port， corresponding a gain of 27.4 dB. In addition， an attenuator is added to suppress oscillations and achieve stable operation.