Wireless power feeding transmission is now in demand in the various fields. Electrical products of this modern age such as mobile phones, laptop monitoring sensors and electrical vehicles are spreading everywhere. Those electric device need to feed frequently because amount of consumed electric power of those devices are gradually increasing. Nonetheless content of battery show signs of leveling off. This is why it is important to develop a method of wireless power transmitting system with high efficiency. Strongly coupled magnetic resonance is the latest type of wireless power transmission technology. The main feature of this technology is the effectiveness in the mid-range that covers many attractive applications. The theory of transmitting efficiency is derived as a function of impedance ratio r and RF frequency ω.© (2011) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.