The device reliability problems of the bonding wire array in gallium nitride (GaN)-basedhigh electron mobility transistor (HEMT) power amplifier become more and more serious due to highvoltage operation, impedance mismatching conditions, and so on. In this paper, both the experimental andtheoretical studies on the electrothermal responses of bonding wire arrays in GaN power amplifier areperformed. By using the finite element method to self-consistently solve the current transport and heatconduction equations, the temperature distributions of the GaN die surface and the bonding wire arrayunder the continuous wave input signals of different power can be obtained, which are consistent with theexperimental results captured by the IR microscopy of the measurement system.