To improve the detection performance of sonar systems, this paper develops a broadband highly sensitive hydroacoustic transducer with a "pyramidal" structure. Selected The single metal plate air column type piezoelectric material is selected as the active material for broadband high sensitivity transducer. The electromechanical equivalence analysis and finite element simulation of the sensitive element are carried out to obtain the preferred range of piezoelectric material size. The "pyramid" shaped transducer sensitive element structure is designed according to the multimode coupling theory. A broadband highly sensitive transducer prototype has been developed by establishing the transducer fabrication process. The test results show that the highest transmission voltage response is up to 182.9 dB, transmission bandwidth is 170 kHz, the highest receiver sensitivity is up to -173.7 dB, receiving bandwidth is 110 kHz, and a -6 dB beam opening angle is 8.1°.