A coupling capacitor structure model for a capacitive wireless power transfer (CWPT) system is built in this paper under the marine environment. It systematically analyzes the influence of seawater parameters (temperature, salinity) on the electrical properties (conductivity, permittivity), which will have a deep effect on the power transfer specialty for underwater capacitive wireless power transfer (UCWPT) system based on the high frequency alternating electric field. With the simulated results analysis, the influence of marine environmental parameters (temperature, salinity) on equivalent seawater capacitance and the equivalent input impedance are summarized in this paper. This paper could be presented as the reference for the coupling capacitor structure design for the UCWPT system.