Aimed at working principle and detecting demand of the Capacitive Micromachined Ultrasonic Transducer (cMUT), a good performance signal processing circuit was designed through analyzing processing methods of transducer’s high frequency weak echo signal, and solved the key problem and primary difficulty which were transducer model transformation and high frequency weak signal conditioning in practical application. Through the testing circuit system, the results showed that the circuit had great linearity and stability, and its bandwidth was , sensitivity was , and resolution was . In the paper, the circuit not only implemented the function of transmission-receiving and high frequency weak signal processing of the cMUT, but also set base for building underwater ultrasonic imaging system of the cMUT.