1-3 piezoelectric single crystal composites with relaxor ferroelectric single crystals and composites as ideal piezoelectric elements in high-frequency transmitting transducers possess the superior characteristics including high piezoelectric constants, ultrahigh electromechanical coupling factors, and low acoustic impedance. A high-frequency wideband transmitting transducer based on 1-3 piezoelectric single crystal composite was designed and manufactured. The properties of piezoelectric single crystal composites were analyzed theoretically, and the transducer structure was optimized via simulation by finite element method. The 1-3 piezoelectric single crystal composite transducer produced has a bandwidth of 160 kHz, while the ripple of the transmitting voltage response does not exceed 3 dB in the frequency range from 250 kHz to 410 kHz. The maximum transmitting voltage response is 178.4 dB. The underwater transmitting performances of the single crystal composite transducer are superior to those of the ceramic composite transducer with the same structure and size. Fabricating high-frequency transmitting transducers using 1-3 piezoelectric single crystal composites can broaden the operating bandwith effectively, and improve the ability of acoustic emission underwater.