In the process of the dynamic wireless charging (DWC) of an electric vehicle (EV), the relative position of the coupling coil changes, causing the problem of constant fluctuations of the charging power, which affects the service life of the battery and bring safety problems. Therefore, a power fluctuation suppression method based on the particle swarm optimization (PSO) algorithm is proposed in this paper. First, based on the LCC-S compensation topology, the transmission characteristics of an EV DWC system are analyzed. Then, a DC-DC conversion circuit is added to the rectifier and voltage regulation part of the receiver, and the double closed-loop control parameters are optimized by the PSO algorithm to achieve stable charging power for EV. Finally, the effectiveness of the proposed method is verified by simulations, and compared with the coupling mechanism design and other control strategies to solve the power fluctuation problem of EV dynamic wireless charging. Moreover, experimental results show that the double closed-loop control optimized by the PSO algorithm in this paper can restore balance within 0.08 s, and the fluctuation range is controlled to within +/- 1% when the coupling coefficient changes continuously.