Wireless charging system for vehicular power batteries is becoming more and more popular. As one of important issues, charging power regulation is indispensable for online control, especially when the distance or angle between chassis and ground changes. This paper proposes a novel power regulation method named Z-Source-Based Pulse-Amplitude-Modulation (ZSB-PAM), which has not been mentioned in the literatures yet. The ZSB-PAM employs a unique impedance network (two pairs of inductors and capacitors connected in X shape) to couple the cascaded H Bridge to the power source. By controlling the shoot-through state of H bridge, the input voltage to H bridge can be boosted, thus the transmitter current can be adjusted, and hence, charging current and power for batteries. A LCL-LCL resonant topology is adopted as the main transfer energy carrier, for it can work with a unity power factor and have the current source characteristic which is suitable for battery charging. And finite element models (FEMs) of transmitter and receiver coils in the LCL-LCL topology are built in COMSOL. From those, corresponding parameters, like self-inductance, mutual inductance and parasitic resistances caused by skin and proximity effect, can be extracted. Additionally, apart from power regulation, employing ZSB-PAM can realize the optimal efficiency in either LCL-LCL topology or the whole charging system. At last, the conclusions are verified by simulations and experiments.