According to the satellite communication application requirements for high-frequency space Traveling Wave Tube(TWT), the experimental results of an E-band continuous wave space TWT are introduced. The parameters of the Folded Waveguide(FWG) slow wave structure are further optimized and the phase velocity taper scheme is adjusted to reform the gain fluctuation, improve the overall efficiency. A prototype tube is fabricated and tested with beam voltage of 14.7 kV and beam current of 74 mA, the experimental measurement results show this prototype is capable of producing an output power up to 85 W and a gain above 40 dB, with the total efficiency over 37% from 71 to 76 GHz. In addition, the TWT has achieved a beam transmission over 98% at the continuous wave operation.