Power supplies and amplifiers constitute the most critical components of underwater communication systems. In this paper, a booster power supply and amplifier circuit are designed for a hydroacoustic communication system. It has the characteristics of high output capacity and small size compared with the traditional transmitter of hydroacoustic communication systems. The improved booster supply is based on the classic Boost circuit for STM32-based digital control power supply. A twice boost is then applied to achieve an output of 100 V for a 10 kΩ load and 70 V for a 100 Ω load. Two secondary boost modules can be connected in series to output a voltage of ±70 V, which supplies power to the amplifier module. The amplifier module has a maximum operating frequency of 1 MHz and maximum output power of 40 W. The dimensions of the final circuit are 120 mm×120 mm×150 mm. We designed a complete hydroacoustic communication experiment to verify that the fabricated high-voltage power supply and amplifier module design are reasonable and feasible and found that the receiver successfully demodulated the baseband signal.