Abstract: To develop a broadband longitudinal vibration transducer which can be used for underwater detection, this paper adopts the method of double incentive design to broaden the bandwidth of the transducer. Setting the target resonant frequency of the transducer as 23 kHz, 42 kHz, based on double incentive resonance frequency equation of longitudinal vibration transducer, this paper carried on the theoretical design of the double incentive longitudinal vibration transducer. On the basis of optimization design by finite element modeling, we simulate its admittance curve and transmission voltage response in air and water. The simulation results show that the resonant frequency of the transducer in air is 22. 56 kHz and 42. 56 kHz, the corresponding admittance is 53. 44 mS and 22. 7 mS, the bandwidth of the transducer in water is 19. 6~43. 6 kHz, the maximum emission response is 147. 1 dB, and the in-band fluctuation is 6. 7 dB. The transducer prototype was made and its resonant frequency in air is 22. 14 kHz and 41. 2 kHz, the corresponding admittance is 47. 4 mS and 17. 7 mS, the work bandwidth in water is 19. 0-43. 5 kHz, and the fluctuation in the band is 8 dB, which is basically consistent with the theoretical design and meets the design requirements.