The present disclosure provides a capacitive micro-machined ultrasonic transducer, a method for preparing the same, a panel, and a device, and belongs to the technical field of ultrasonic imaging. A capacitive micro-machined ultrasonic transducer includes a first electrode, a vibrating diaphragm layer and a second electrode that are arranged in order from bottom to top, a cavity existing between the first electrode and the vibrating diaphragm layer, in which the capacitive micro-machined ultrasonic transducer further includes a third electrode located on a surface of the vibrating diaphragm layer proximate to the cavity, an orthogonal projection of the third electrode on the first electrode covers a part of an orthogonal projection of the cavity on the first electrode. The technical solution of the present disclosure can realize the conversion of the frequency of the ultrasonic waves emitted by the capacitive micro-machined ultrasonic transducer.