Abstract: Aiming at the problem that the power factor and efficiency of the modulation strategy of bidirectional dual LCC wireless charging system based on full bridge topology decrease seriously under light load conditions, this paper proposes a half-bridge modulation strategy on the basis of not changing the full bridge structure. Firstly, the on state efficiency of the bidirectional double LCC compensation circuit is modeled, and the key variables and constraints affecting the efficiency are analyzed quantitatively, thus providing a theoretical basis for the optimization of modulation strategies; On this basis, the paper analyzes the working principle of the proposed two-sided half bridge modulation strategy, the optimization relationship of the positive conduction angle and the realization conditions of soft switching in detail, and proves that the strategy can significantly reduce the external shift phase angle while ensuring the zero voltage switching (ZVS) of the switching device, thus effectively improving the power factor and operating efficiency of the system; Finally, A 3.3 kW bidirectional wireless power transfer (BD-WPT) system prototype is built for comparative experiments. The experimental results show that the half bridge modulation strategy proposed in this paper can achieve the highest efficiency of 95.6% under light load conditions of 1/4 full load and below, and can achieve significant optimization effect when the output voltage changes in a wide range.