The transmitting power of traditional CLASS V flextensional transducer is not high. To solve this technical problem, the application of new active material, structural design and parameter optimization methods are adopted. The relaxed ferroelectric single crystal piezoelectric material polarized along the [011] c direction is effectively used, and its piezoelectric coefficients $d_{32}$ and $d_{31}$ are high. The displacement amplification structure is added, and the material and size of the structure are optimized. Finally, the working frequency of the transducer is reduced and the power is increased. The active material is more fully utilized, and a technical way to improve the power of the transducer is provided.