A novel thermoelectric and capacitive power sensor with improved dynamic range based on GaAs monolithic microwave integrated circuit (MMIC) technology is proposed in this letter. This power sensor is designed and fabricated using GaAs MMIC process and MEMS technology. A MEMS cantilever beam is introduced and monolithically integrated as a capacitive power sensor to improve the overload capacity and the dynamic range at the cost of sensitivity. The measurement results verify the role of the MEMS cantilever beam. Another advantage of this power sensor consists in compatibility with MMIC devices and other planar connecting circuit structures with zero dc power consumption.