Abstract: The bandwidth of the Class IV flextensional transducer is narrow for its high mechanical quality factor. For improving its bandwidth capability, a flextensional transducer with major axis lengthened is proposed by the theory of nmltiple-mode-coupling based on the oval shell. The transducer driven by novel relaxor ferroelectric single crystal lead magnesium niobate-lead titanate (PMNT) is designed and analysed using finite element software ANSYS and a prototype of the transducer is developed. The transmitting voltage response of the transducer reaches to 136 dB with ripple 7.8 dB from 1.6 kHz to 16 kHz. Based on the theoretical analysis and experimental results, it proves that the flextensional transducer with major axis lengthened has a much broader bandwidth than the Class IV flextensional transducer combing with the advantages of low frequency and high response.