There are many advantages of broadband transducers, such as reduction of signal distortion, widening the security about information transmission, and reducing the ratio of false codes. The use of three 32-mode single crystal pieces, a thin light beryllium alloy head mass, and a thick heavy tungsten alloy tail mass, can expand the bandwidth of the middle-frequency transducer. The one-third finite element model of transducer was set up with ANSYS software and the structure of the transducer was optimized. A final transducer was designed, fabricated and measured, and its longitudinal size is about 23mm. The bandwidth of the transducer is 16kHz–91kHz, in which the ripple of the transmitting voltage response does not exceed ±3.5dB. There are several conclusions from the research: the bandwidth of tonpilz transducers can be expanded by the use of single crystal pieces, beryllium alloy head mass and tungsten alloy tail mass; and it gives a method to achieve the broad-band projecting performance of middle-frequency transducers.