Abstract: In this paper, a 170 GHz~260 GHz solid-state amplifier module based on gallium nitride chip is designed. A waveguide-to-coplanar waveguide transition structure is used by the module where a wedge-shaped waveguide iris is inserted into a standard rectangular waveguide to achieve a highly compact and low-loss transition. The simulation results show that the transition has an average return loss of better than 20 dB over the entire waveguide band, with an insertion loss is less than 0.12 dB. Furthermore, a choke groove structure is introduced at the input and output flanges to suppress signal leakage that may occur during module cascading. The actual test results show that the amplifier module achieves a small-signal gain of more than 7.6 dB over the frequency range of 170 GHz~260 GHz, with output powers greater than 4 mW at all frequencies. Furthermore, the module achieves a maximum output power of 12.8 mW at 213 GHz, with a PAE of 8.7%.