Abstract: In order to improve the low-frequency broadband performance of the barrel-stave transducer, a new structure of four-beam square barrel-stave transducer with decoupling end caps is proposed. The structure at the end of the PZT longitudinal vibrator is an elastic auxiliary beam, which is connected with the concave flexural beam to form a composite flexural beam. In order to reduce the adverse effects of the auxiliary beam on the acoustic radiation, square decoupling end caps driven by longitudinal driver are designed as new radiating surfaces. The modal analysis is made at first, which shows that frequency spacing between the available first five class modes could be adjusted by several characteristic structural parameters effectively. An optimal design of the transducer is presented with the overall geometric size 140 mm×140 mm×396 mm. Then the admittance and transmitting voltage response are simulated and analyzed. It is shown that the maximum transmitting voltage response is greater than 145 dB. The -6 dB frequency range is from 1.5 kHz to 4.3 kHz, and -10 dB frequency range from 1.5 kHz to 8 kHz. The low-frequency, broadband and high power performances of the transducer are confirmed by these results.