An integrated multi-beam traveling wave tube based on Multi-Corrugated Waveguide SWS （MCW） is investigated by simulation and cold test in this paper. The MCW SWS is adopted here for its high coupling impedance and its natural multi-beam tunnels， then a Ka-band integrated three-beam traveling wave tube amplifier with MCW is designed. The interaction circuit is fabricated by CNC milling with oxygen-free high conductance copper. The cold test is found to be in great consistency with simulation and the S₁₁ is lower than -15 dB from 32~39 GHz. Using CST PIC Studio， the PIC simulation is performed for the interaction circuit with 50-periods SWSs and three beams with 12.9 kV voltage and 67 mA current. The simulation shows significantly better output power， gain， and electronic efficiency than DCW. The maximum output power is about 132.8 W with corresponding electronic efficiency of 5.12% and gain of 41.2 dB. The high power and high efficiency performance of the proposed MCW TWT provides potential application for point-to-multipoint transmission based millimeter-wave wireless system.