Abstract: The broadband matching network design of underwater acoustic transducer is one of the key technologies for broadband sonar system which can effectively reduce the power loss, expand the working bandwidth of the transducer and improve the distortion of the transmitted waveform. In this paper, a broadband matching network design for multi-resonant mode transducer with the real frequency method is proposed. For underwater acoustic piezoelectric ceramic transducer, the impedance varies with the frequency and difficult to be expressed by the analytical function. Therefore, it is difficult to achieve good broadband matching performance in a wide frequency range. The traditional broadband matching technology need complex analytical theory and analyzes the equivalent circuit of the transducer. In fact, the single inductor matching and multi-resonance method often used for underwater acoustic transducer broadband matching design, however, the actual matching effect cannot achieve the desired. In the radio field, the theory and method of broadband matching has been well developed, combined with computer aided design (CAD) technology, a series of broadband matching numerical methods applied in the antenna broadband and microwave amplifier matching. The design process is accomplished with computer aided and without equivalent circuit of the load. Taking this advantage, the real frequency direct computational technique is utilized for broadband matching network of underwater acoustic transducer. Firstly, the matching principle of the transducer is briefly discussed; and then the theory of Simplified Real Frequency Technique (SRFT) is discussed. Secondly, the matching network of the pressure pipe transducer is designed. The nonlinear least squares algorithm is used to optimize the transducer power gain (TPG), with the continued fraction expansion method to synthesize wideband matching network. Finally, the matching performance is tested in anechoic pool. The results show that the broadband matching network can improve the transmission efficiency and expend the bandwidth of the transducer. In the same experimental conditions, compared with the transmitter without matching, the source level of the system increased about 10dB. Moreover, compared with the transmitter with narrowband matching circuit, the work bandwidth of the transducer is extended about 64%