In the context of wireless power transfer (WPT) systems, the lack of direct communication between the primary and secondary sides necessitates the synchronization of the drive signal for synchronous rectification through current detection. This paper introduces a zero-crossing detection (ZCD) method that enhances precision by employing digital sampling interpolation. This approach enables high-precision zero-crossing detection even with low-speed ADC and demonstrates insensitivity to current jitter near the zero-crossing points. The paper analyzes the primary interference sources and their frequency bands in the current signal while examining the amplitude-frequency characteristics of spline interpolation. Based on the effect of the interpolator on the input signal, design guidelines for the interpolator parameters are provided. Furthermore, an efficient circuit implementation of the interpolator is achieved, where the computational process involves only addition and subtraction, imposing minimal performance demands on the controller. Finally, an experimental platform was constructed to verify the effectiveness of the proposed method.