Wireless Power Transfer (WPT) technology for charging Electric Vehicle (EV) batteries is promising technology. System performance improvement and reducing Electromagnetic field (EMF) leakage are the key factors in designing an optimum charger. In this paper, adding ferrite disk to the WPT resonator is intensively studied. Three case studies are proposed, including coils only without ferrite, ferrite disk at the transmitting side only, and ferrite disks are used with the two coils. Finite Element Method (FEM) software is used for designing 3 kW-class, 20 cm transfer distance, 85 kHz charger. The simulation results are recorded and compared with regard to the system coil-to-coil efficiency and the EMF levels above the receiving coil and inside the air-gap. The results show that adding ferrite disks is significantly enhanced the system performance as well as reduced the EMF leakage surrounding the charger.