Wireless power transfer (WPT) systems utilizing zero phase angle (ZPA) control can maintain stable output independent of transmission distance. However, ZPA control requires the inverter to keep voltage and current strictly in phase, causing losses and reducing overall system efficiency. To address this issue, this paper introduces a soft-switching phase-shift control strategy to reduce inverter losses and improve system efficiency. First, an equivalent circuit model of a series–series (SS) compensate WPT system is established, and its operating modes under soft-switching phase-shift control are analyzed. Then, the loss characteristics of both ZPA and soft-switching phase-shift control are derived and compared. Finally, an implementation method is presented, and an experimental prototype is built. Results show that under a full-load output of 58 W, the system with soft-switching phase-shift control achieves a transmission efficiency of 97%, and the overall system efficiency is improved to 87.8%, representing 2% higher than with ZPA control.