Abstract: This paper introduces an engineering realization of a Ka-band 400 W GaN highly linear solid-state power amplifier. 64 GaN power chips are used for power synthesis by combining microstrip bridge and waveguide power division / synthesis network. The continuous wave saturated output power of the power amplifier is greater than 400 W in the working frequency band of 2 GHz. Radio Frequency predistortion technology is applied, and the third-order intermodulation is better than -33 dBc and the improvement is up to 9 dB. To meet engineering and productive requirement, a good heat dissipation is designed. The control and maintenance functions are provided, the reliability and practicability meet the engineering requirements.