In order to improve the sensitivity characteristics of the on-line MEMS microwave power sensors, a novel type of MEMS microwave power sensor with double cantilever beams was designed. The measured electrodes and the anchors were located on opposite sides of the central signal line in this structure. A lumped equivalent model of double cantilever beam circuit was established, and the microwave characteristics of the double cantilever beam were studied. A pivot-type static model of double cantilever beam was established. The overload power and the sensitivity of this novel cantilever beam structure were theoretically analyzed. The results show that the sensitivity of the novel double cantilever beam structure is 6-8 times higher than that of the traditional single cantilever structure in which the measured electrode and the anchor are located on the same side of the signal line. It solves the disadvantage of the low sensitivity of the capacitive microwave power sensor to a certain extent.