The invention discloses a multi-mode 
broadband high-power directional transmitting 
longitudinal vibration underwater acoustic 
transducer, which relates to the field of 
underwater acoustic transducers,and comprises a 
longitudinal vibration transducer vibrator with a flexible ring, a square cylindrical structure 
resonant cavity shell, a decoupling support structure and a 
tail sealing end cover, wherein the 
longitudinal vibration transducer vibrator with the flexible ring is composed of a 
front cover plate with the flexible ring, a piezoelectric 
ceramic crystal pile, a stress screw rod and a rear cover plate. According to the liquid cavity 
coupling principle, a liquid 
coupling cavity in a 
square cylinder structure is designed at the front end of a 
front cover plate of a vibrator of the longitudinal vibration transducer with the flexible ring, and a new 
resonance peak can be generated between two resonances of the double-cover-plate longitudinal vibration transducer. The beneficial effects of the invention are that the multi-mode 
broadband high-power directional transmitting longitudinal vibration 
underwater acoustic transducer is wider in 
frequency band, and can achieve 
broadband transmission in a range of medium and low frequencies from 2.5 Hz to 7.5 Hz; backward 
radiation in a working 
frequency band is small, and the unidirectional 
radiation capacity is high; the structural size can be adjusted according to actual 
engineering requirements, and the deep-water 
working capacity, the adaptability and the flexible arrangement are achieved.