With the increase in maritime activities, traditional communication methods can no longer meet the needs of today’s maritime work, and the use of unmanned aerial vehicle(UAV) relay communications in marine scenarios has attracted more and more attention. In this paper, A long-distance three-node two-hop UAV relay system for maritime users is investigated. The UAV aerial relay node first transmits an energy-carrying radio frequency (RF) signal to the maritime user node, which then harvests energy and sends data information back to the UAV aerial relay node, which in turn forwards it to the land node. Considering the peculiarities of maritime communication channels, a novel land-air-maritime communication channel model is proposed. Utilizing Zero-Forcing/Zero-Transmission (ZFR/ZFT) technology, a precoding matrix for the aerial relay node is designed, followed by simulation and emulation, the performance of the channel is tested in the case of different transmission power of relay nodes or different number of antennas of relay nodes.