Abstract: This paper proposes a stub-loaded gallium nitride field-effect transistor (GaN-FET) phase shifter with ultra-low DC power consumption and high power handling capability. The phase shifter consists of multiple micro-strip stubs with high impedance and GaN-FET loaded. By analyzing the circuit model of the single stub-loaded GaN-FET phase shifter in detail, the formulas for insertion loss and phase shift are obtained. Then, as the basic element, the GaN-FET phase shifter using multiple stubs is developed, which can operate at the predefined frequency band. Due to the employment of the high-Z micro-strip stub, the proposed phase shifter can handle high input power. Following the design theory, the GaN-FET phase shifter using multiple stubs is designed, fabricated and measured. The tested results show that the phase shifter achieves the phase shift of 30° and 60° by controlling the GaN FETs within the frequency range of 9.2 GHz to 9.8 GHz. In addition, the power handling capability is over 10 W, insertion loss less than 1 dB and DC current for control less than 6 μA.