Abstract: Factors that affect transmission power and efficiency of magnetic coupled wireless power transmission system based on self-resonance coils and magnetic coupled wireless power transmission system based on series capacitor tuning were obtained according to equivalent circuit models, and frequency characteristics of the two systems were analyzed. The experimental results show that there is no frequency splitting in the magnetic coupled wireless power transmission system based on self-resonance coils with larger transmission power, while there is frequency splitting in the magnetic coupled wireless power transmission system based on series capacitor tuning when distance between receiving coil and sending coil is less than a critical value, because resonant frequency is influenced by coil equivalent shunt capacitance and external series capacitance.