The multi-stage GaN amplifier with dual output power was explained for the application of microwave communication and power transmission. For the compact transmitter, single-tone and time-division operation is adopted in this study. The maximum output power of 91.8 W and the PAE around 55.4 % were obtained at 2.1 GHz in the high power transmitter operation. In the low power transmitter operation, the 4Mbps symbol-rate QPSK signal was achieved under the 19.2 W with 35 % PAE. By combining with a multi-stage rectifier in the receiver, the compact microwave communication and power transmission system can be realized.