Aiming at the key problems of single-stage LC resonant electric-field coupled underwater power transfer(ECPT)system with low output power, small resonance capacity and large frequency drift, a more suitable wireless power transfer system in seawater environment is designed. The system is based on the CLC-S tuning network, which combines the advantages of high efficiency and high frequency of the class E amplifier, and achieves a large power output. The capacitance value of the coupling mechanism in seawater environment was solved by Maxwell finite element simulation software. Through the experiment of underwater coupling mechanism, the influence law of load quality factor Q and normalized frequency μ on underwater wireless power transfer system is analyzed. The experimental results provide an important reference for the design of underwater ECPT systems in the future.