Abstract: A high linearity gallium arsenide heterojuncion bipolar transistor ratio-frequency power amplifier operating at 5. 15 GHz~5. 85 GHz is designed to meet the equipment requirements of WiFi 6. In order to ensure the stability of the static operating point of the power transistor under high signal and high temperature, a new active adaptive bias circuit is adopted. A novel ratio-frequency power detection circuit is designed and improved to reduce the power consumption of the ratio-frequency system. The output matching network is optimized according to the influence of each harmonic component. The simulation results show that the small signal gain of the radio-frequency power amplifier chip reaches 32. 6 dB. At 5. 5 GHz, 1 dB compression point power is 30. 4 dBm ,the additional power efficiency exceeds 27. 9% .When the output power is 26 dBm, the third-order intermodulation distortion is lower than -40 dBc. The measured data shows that the small signal gain is greater than 31. 4 dB. At 5. 5 GHz, 1 dB compression point power is 29. 06 dBm. When the output power is 26 dBm, third-order intermodulation distortion is lower than -30 dBc. The second and third harmonic component are suppressed to -30 dBc and -45 dBc respectively with 20 dBm output power.