The invention discloses a broadband balance power amplifier based on GaN. The broadband balance power amplifier based on the GaN comprises a Lange coupler, a microstrip transmission line, a Banding metal wire, a filter inductor, a stabilizing resistor and a wide band gap GaN-based HEMT. A biasing circuit of the power amplifier comprises a T-shaped connector, the microstrip transmission line, the filter inductor, the stabilizing resistor and the GaN-based HEMT, the GaN-based HEMT (H) is an HEMT pipe core with the type of NRF01-02a, and a four-line 3dB coupling Lange coupler with the characteristic impedance of 50 ohms is selected and used as the Lange coupler. The broadband balance power amplifier based on the GaN is simple in structure and low in cost, the Lange coupler is adopted for constructing the structure of the balance power amplifier, a multi-section impedance matching technology is adopted for designing an input/output matching network, the power amplifier broadband characteristics are achieved, and within the 115-315 GHz frequency band, the power amplifier linear gain is larger than 12 dB, and the saturation output power is larger than 8 W.