This paper presents the fabrication and cold-test of a three-slot-staggered-ladder coupled cavity slow wave structure (CC-SWS) along with high power input-output couplers and RF windows in W-band. The SWS is fed by a rectangular waveguide coupler which is made up of a three-order step-transform rectangular waveguide placed on the short edge of the input cavity. Firstly, the dispersion, interaction impedance, transmission property and beam-wave interaction are studied using the simulation method. It is shown that the traveling wave tube (TWT) with a three-slot-staggered-ladder CC-SWS is able to provide a sat-uration output power of more than 1000 W in the frequency range of 91-96GHz, and the maximum saturated output power can reach 1125W at 94 GHz. Secondly, the CC-SWS is fabricated by the high-precision CNC milling and fixed in a nonmagnetic stainless steel housing. Test results of the fab-ricated CC-SWS with couplers and RF-windows are presented, showing the S11 < -10 dB in the frequency range of 90GHz to 100GHz. Therefore, the three-slot-staggered-ladder CC-SWS is a promising slow wave circuit of high power W-band TWT.