Abstract: Electric-field coupled power transfer（ECPT） systems employ high frequency electric field as energy medium to transfer power wirelessly. In practical applications, the electrical equipment has the need of a stable operating voltage. This paper derived the general constraints on resonant networks operating at four states for constant output, respectively. And then the three and four order resonant circuits with constant output were presented. The output gains of these resonant circuits were calculated and the total harmonic distortion as well as parameter sensitivity was analyzed. Accordingly, the configuration of ECPT systems based on composite resonate circuits with constant output was proposed and the parameter design method was presented. Finally, the transfer characteristics of the proposed system and accuracy of the design method have been verified by simulations and experimental results.