For the WPT system with multiple transmit coils, the coupling channel is filled with energy transfer magnetic field. Although the multi-transmit coil structure improves the system’s anti-displacement ability, the increased contact area also brings the risk of metal foreign objects intrusion. Therefore, based on the principle of detecting changes in the magnetic field, a metal foreign object detection method is proposed to eliminate the detection blind area. By introducing a dual-layer detection coil group, a metal foreign object detection method without blind area is achieved. First, the basic principle of metal foreign object detection is analyzed, and the detection of metal foreign objects is achieved by detecting the change in the induced voltage of the detection coil. Then, the structure of the detection coil group is introduced, including the horizontal detection coil group and the vertical detection coil group, and the detection principle is explained. Finally, the proposed wireless charging system metal foreign object detection method is verified by constructing a radio energy simulation platform. The results show that when the metal foreign object is located at different positions of the detection coil, the horizontal detection voltage, vertical detection voltage, and central detection voltage will change, thereby verifying the effectiveness of the proposed metal foreign object detection method.