In order to meet the practical demand of the wireless charging for electric vehicles, a constant current control method is proposed. The model of the magnetic coupling resonance inductively coupled power transfer (ICPT) system based on LCL-S type is established, and its operating characteristics are analyzed. Then, according to the output characteristic curve of the secondary current and the transmission efficiency characteristic curve, the frequency range of the system is determined. And this interval is used as the frequency modulation area of the system constant current operation. The advantages and disadvantages of various power control methods are compared. Furthermore, a constant current control strategy is proposed, which is the combination of variable frequency control and phase shifting voltage regulation. Control program of the P feedback is designed. Through experiment, the constant current control effect is verified when the load is different. The experiment shows that the control strategy can realize the non-static difference and the fast response control without overshoot.