Abstract: Broadband matching of piezoelectric underwater acoustic transducers is one of the key technologies in transmitter design. Good broadband matching can reduce the power capacity requirements of the transmitter. For piezoelectric transducer-based broadband transmitters, the mathematical model of the power amplifier based on sinusoidal wave pulse width modulation (SPWM) is first established, and the conventional first-order and multi-order broadband matching topologies are analyzed. Secondly, based on the derivation of the mathematical model of the power amplifier, it is derived that using current minimization as the objective function can ensure the minimization of transmitter loss, and multiple constraints—including the transmitter source level, in-band flatness, and harmonics—are established. Thus, an optimization algorithm for the matching parameters of underwater acoustic transmitters based on a single objective and multiple constraints is proposed. Finally, relevant experiments were conducted using the matching parameters calculated by this optimization algorithm. The experimental verification results show that the optimized matching parameters enable the transmitter to meet each constraint condition and ensure that the output current of the power amplifier is basically consistent with the optimized calculated current, with an error not exceeding 10%.