The PCB self-resonant coil studied in this article is suitable for the transmitting coil, receiving coil, and relay coil of multi-relay WPT systems. Firstly, the structure of the designed PCB self-resonant coil was introduced, and then a distributed equivalent model of the self-resonant coil was established. Secondly, the three resonance parameters required for designing the coil were analyzed and calculated using a lumped model, and mathematical optimization was carried out based on this. Finally, a PCB self-resonant coil sample was made, and the experimental results verified the good consistency of this method.