In order to extend the transmission distance and improve the transmission efficiency of the traditionalwireless power transmission(WPT)system composed with the transmitting and receiving coil resonators based onmagnetic resonance coupling，we proposed an effective method to add a magnetic core between repeating coil andreceiving coil based on the single repeating three coils mode. This paper deduced a mathematical expression of thetransmission efficiency，and built a model by the circuit theory，and also simulated the transmission system addedwith the magnetic core between repeating and receiving coil. Then we selected the flat magnetic core for test. Atlast，we verified the feasibility of the proposal by actual experiment.