This paper presents a wireless power transfer system with a planar runway-type transmitting coil and a circular receiving coil. The circuit topology and coupling mechanism of system are introduced. A mutual inductance calculation method based on Nieman’s formula is brought up. The coupling mechanism’s charging area are optimized and analyzed. Using this method, mutual inductance, power, and efficiency as functions of position are calculated. In-depth research is conducted on these calculations. Results from numerical calculations demonstrate that the proposed system can broaden the effective wireless energy transfer area and have the ability for multiple loads. It also improves the system’s tolerance for position deviations, maintaining load power and efficiency at 89% of the peak value even with a 20 cm displacement along the x-axis.