A 71-76GHz traveling wave tube amplifier is successfully developed to meet the demand of future high-data-rate wireless communication, breaking through a series of key core technologies including beam-wave interaction circuit, two-stage depressed collector, electronic power conditioner and module integration. The test results show that the amplifier is capable of providing more than 63.1W CW output power,37.8dB saturated gain,23.6% total efficiency in 71-76GHz band. The 1dB compression point is over 21W. The third-order intermodulation is <-12.2dBc at 6dB OBO. The dimension and weight of the amplifier are $379\boldsymbol{mm}^{*}200\boldsymbol{mm}^{*}63\boldsymbol{mm}$ and 6.5kg respectively with -48VDC electronic power conditioner embedded.