Abstract: A design to broad the transducer's bandwidth by coupling the flexural vibration of the front mass and the longitudinal vibration of the transducer is proposed.The transducer is analyzed by the finite element simulation software ANSYS, and the optimum design dimensions of the transducer is obtained through analysis. Experiments verified that the bandwidth(-3dB)of the measured admittance and transmitting voltage response can be up to one octave. Since the transducer has a low compression resistance, a high hydrostatic pressure experiment is specially made to show that the transducer can at leas endure a hydrostatic pressure of 8 MPa.