Abstract: The emission array of the deep-water multi-beam sounder has more than 800 independent emission elements, which can realize high-power emission with a beam width of 1°×1° along the track direction. Due to the need for phased emission, each transducer element corresponds to an independent transmission channel, so more than 800 independent transmission channels are required. This paper introduces the principle of the transmitting array of the deep-water multi-beam sounder and then, based on the mechanical specification of compact peripheral component interconnect (CPCI), adopts a custom low-voltage differential signal (LVDS) bus, a phased transmitter with 840 channels and independently controllable amplitude and delay has been realized. Due to linear transmission technology, the total power consumption of the transmitter is large. Therefore, heat dissipation design is implemented for the chassis to solve the heat dissipation problem. The transmitter subsystem has the characteristics of accurate beam control directivity, good real-time performance, and high transmitting power. Practical application results at sea show that the system performance meets the design requirements.