Abstract: A innovative design of a "Fish-mouth" flextensionaltransducers is proposed, it is utilized a elliptical shell with variable height. The special shell is provided with amplitude amplification and weighted height amplification effect that is called "double-amplification" effect. A prototype of t he Terfenol-D "Fish-mouth" flextensional transducer is developed. Theoretical analysis and experiments in lake are showed that the "Fish-mouth" flextensional transducer has lower resonant frequency:about 1.1 kHz, wider frequency band:Q factor for -3 dB bandwidth less 3,than 3, transmitting current response level:182 dB. A free-flooded cavity with compliant material is used to achieve depth capability.