In this work, a novel high overload Ka-band power sensor with a Micro-electro-mechanical system (MEMS) cantilever beam is investigated in order to improve the measurement dynamic range and the bandwidth.The fabrication of the Ka-band power sensor is divided into front side and back side processing with a combination of surface and bulk micromachining of GaAs.The low-power measurement reveals that the terminating-type sensitivity is close to 0.081, 0.076 and 0.072mV/mW at 34, 35 and 36GHz, respectively. The high-power measurement indicates that the capacitivetype sensitivity is around 4.9fF/W at Ka-band. The overload power measurements show that the MEMS cantilever beam can improve the dynamic range by increasing the top end of the range into no less than 200mW, and enhance the bandwidth by increasing the top end of the range into no less than 36GHz. There is an important reference value to achieve the high overload and wide frequency band for the thermoelectric microwave power sensors.